PC Randomly Restarts? Find Which Cause Is Yours (2026)

A random restart wipes the screen you needed to read. It leaves the log alone. Windows writes down the restarts it did not plan, and that record sorts the problem before you open the case.

There are four kinds. Something asked for the restart. A blue screen came and went too fast to see. The power dropped or the board reset. Or the PC froze and someone held the button. Each goes to a different fix. The tests past this point cost evenings—a proper memory test runs overnight—so I sort the restart first. It takes five minutes.

Pull the last few restarts out of the log

Press the Windows key, type powershell and press Enter. Paste this line and press Enter again:

Get-WinEvent -FilterHashtable @{LogName='System'; Id=41} -MaxEvents 5 | ForEach-Object { [pscustomobject]@{ Time = $_.TimeCreated; BugcheckCode = $_.Properties[0].Value; Hex = '0x{0:X}' -f $_.Properties[0].Value; PowerButton = $_.Properties[6].Value } }

Each row is one time Windows came back up without a clean shutdown. That is event 41 from Kernel-Power, and Microsoft’s wording for it is “The system has rebooted without cleanly shutting down first.” Find the row whose Time matches your restart and read the numbers beside it.

If PowerShell answers in red with “No events were found that match the specified selection criteria”, the log holds no event 41 at all. Start at the planned-restart check.

Event Viewer shows the same events in the System log as Critical entries from Kernel-Power, if you would rather click. The two numbers that matter sit deep inside each event there, which is why I use the command. All three commands on this page run without administrator rights. I checked them on my own desktop on September 28, 2026, on Windows 11 Home 25H2 (build 26200.9457).

A restart something asked for

Rule out the scheduled restart before you blame hardware:

Get-WinEvent -FilterHashtable @{LogName='System'; Id=1074} -MaxEvents 5 | Format-List TimeCreated, Message

Microsoft logs event 1074 when a program or a person starts the restart. The message names the process that asked and ends with its reason. On my build, a restart picked from the Start menu names StartMenuExperienceHost.exe. Windows Update’s restarts name MoUsoCoreWorker.exe or TrustedInstaller.exe, with a reason that begins “Operating System” and ends “(Planned)”. An installer you ran names its own setup file.

A 1074 at the time of your restart means nothing broke. Microsoft says a PC “might need to restart to finish installing the updates” and gives active hours as the control. Open Start > Settings > Windows Update > Advanced options > Active hours, then pick Automatically or Manually. Set them to the hours you sit at the machine.

The stop code picks the page

A BugcheckCode above 0 means Windows hit a stop error and restarted before you could read the blue screen. Event 41 stores that code in decimal. Microsoft’s own example is 159, which is 0x9F in the hexadecimal that most stop-code references use, and the Hex column in the command does the conversion. Find your number here and go to its page.

• 26, which is 0x1A MEMORY_MANAGEMENT: memory management BSOD
• 80, which is 0x50 PAGE_FAULT_IN_NONPAGED_AREA: page fault in nonpaged area
• 239, which is 0xEF CRITICAL_PROCESS_DIED: critical process died
• 278, which is 0x116 VIDEO_TDR_FAILURE: GPU driver crash fix
• 292, which is 0x124 WHEA_UNCORRECTABLE_ERROR: the code 0 checks below, which cover heat, overclocking and memory; a processor that is starting to fail, the last cause Microsoft names, takes a swap to rule out
• 313, which is 0x139 KERNEL_SECURITY_CHECK_FAILURE: kernel security check failure
• 456, which is 0x1C8 MANUALLY_INITIATED_POWER_BUTTON_HOLD: if it froze first

For any other number, take the Hex value to Microsoft’s Bug Check Code Reference, which lists the common codes and links a page for each. For a code it lacks, Microsoft points to WinDbg’s !analyze -show command.

Two other places hold the same crash. Event 1001 from Windows Error Reporting, when it is there, reads “The computer has rebooted from a bugcheck” and gives the code in hex with the path of the dump file. The dumps sit in C:\Windows\Minidump and C:\Windows\MEMORY.DMP; the memory management guide shows how to open one in WinDbg.

The same code on every restart means that page is your fix, and you can stop reading here.

A code that changes from one restart to the next is a different signal. PSU failure symptoms lists blue screens that name a different driver each time among a failing supply’s signs, so a moving code goes through the code 0 checks from the top.

Keep the next blue screen on screen

If event 41 holds a code and no blue screen ever stayed up, the Automatically restart box is checked. On my desktop the registry value behind it, AutoReboot, read 1. Clearing it costs nothing, and the next stop code stays up until you restart the PC yourself.

1. Press Windows+R, type SystemPropertiesAdvanced and press Enter. System Properties opens on the Advanced tab.
2. Under Startup and Recovery, click Settings.
3. Under System failure, clear Automatically restart and click OK.
4. Restart once so the change takes effect.

Microsoft recommends this when a blue screen shows a code that event 41 did not keep. Write the code down when it appears.

If the PC still restarts instantly with the box cleared, and no blue screen ever shows, the machine is going down before Windows can stop it. That is the next section.

A code of 0 means power, heat or an overclock

This is the branch that sends people shopping, and Microsoft’s own article is specific about it. When event 41 is missing or its codes are 0, it says something stopped Windows from writing an error code. The first four checks it lists are the ones that apply to a home PC, and they are overclocking, memory, the power supply’s wattage and overheating. I work them cheapest first.

One false alarm to clear before you start. If every value is 0 and the System log also holds event 46 from volmgr, “Crash dump initialization failed!”, a blue screen may have happened with nowhere to save its code. Microsoft’s fix for that case is to check the page file, because the page file is where the dump goes.

1. Look at the outlet. It takes a minute. Microsoft’s first causes are the dull ones: a desktop that was unplugged or caught a power outage, a laptop whose battery ran flat. If a lamp on the same power strip flickered when the PC went down, the problem is the wall.

2. Put everything back to stock. Any CPU overclock, Precision Boost Overdrive or Curve Optimizer offset, any GPU overclock or undervolt, and the XMP or EXPO memory profile. Microsoft’s first hardware check is to disable overclocking, and a memory profile is a factory overclock that the memory management guide tests with a ten-minute JEDEC run. Use the PC normally for a day. If the restarts stop, the tuning was the cause.

3. Watch temperatures under the load that triggers it. A CPU that reaches its emergency limit cuts power with no blue screen, and a cut like that leaves a code of 0 behind. How to check CPU temp covers the tools, CPU overheating sorts the cause by when it happens, and GPU overheating does the same for the card.

4. Ask the hardware what it reported. Two minutes:

   Get-WinEvent -FilterHashtable @{LogName='System'; ProviderName='Microsoft-Windows-WHEA-Logger'} -MaxEvents 10 | Format-List TimeCreated, Id, Message
   

   WHEA is the Windows hardware error architecture, and WHEA-Logger is the source it writes its error records under in the System log. PowerShell prints “No events were found that match the specified selection criteria” in red, and here that is the good result. Entries at the times of your restarts point at the causes Microsoft lists for the fatal version, bug check 0x124: heat, an overclock, bad memory or a processor that is starting to fail.

5. Reseat the power cables with the PC off. The 24-pin, the CPU’s 8-pin, and every graphics card connector, pushed in until the latch clicks. That includes the 12V-2x6 plug on a newer card.

6. Check the wattage. Microsoft calls out the machine that gained a newer processor, more memory or more drives on the same supply. Put your parts into the PSU wattage calculator; on an RTX 50-series card, what PSU each card needs has the figures.

7. Test the memory overnight. Microsoft’s list says to check the memory, and switching off XMP or EXPO in step 2 only tests the profile. Boot MemTest86 from a USB stick and let it run through the night; the memory management guide explains how to read the result and name a bad stick.

8. Then the power supply itself. With a code of 0, no WHEA entries, stock settings that did not help, sane temperatures and a clean memory test, the supply is the suspect left. PSU failure symptoms shows how to watch the 12V rail under load and why a swap with a known-good unit settles it.

Steps 1 through 7 cost time and nothing else. Step 8 is the first that can cost money, which is why it comes last.

If it only restarts in games

A game loads the CPU and the graphics card at the same time, so a restart that only comes mid-match points at heat and power first. Read event 41 the same way. A code of 0 goes through the checks above. A code of 278, 0x116 VIDEO_TDR_FAILURE, means the graphics driver stopped responding and Windows failed to reset it. Microsoft’s page for that code says the GPU is usually busy with heavy graphics work when it happens, typically during gameplay. The GPU driver crash fix works that from a clean reinstall down. If the screen instead blinks black and comes back with “Display driver stopped responding and has recovered”, the PC never restarted, and that is the same page’s milder case.

If it froze first

A PowerButton value above 0 means the power button was held down, and Microsoft writes that value when a restart is forced that way. The restart was yours. The fault is the freeze before it. Microsoft’s quick test for a hard hang is the Caps Lock key: if its light does not change when you press it, the machine has probably locked up. BugcheckCode 456 (0x1C8) tells the same story on a PC configured to save a dump when the button is held.

It restarts when you shut it down

A PC that restarts the moment you pick Shut down has a shutdown problem. Run the event 1074 command first, because it names what started the restart. Then turn off Fast Startup, following Dell’s steps. Open Control Panel > Hardware and Sound > Power Options > Choose what the power buttons do > Change settings that are currently unavailable, and clear Turn on fast startup (recommended) under Shutdown settings.

Sources

• Microsoft Learn, Event ID 41 The system has rebooted without cleanly shutting down first (updated February 12, 2026)
• Microsoft Learn, Bug Check Code Reference (July 15, 2025)
• Microsoft Learn, Bug Check 0x116 VIDEO_TDR_FAILURE
• Microsoft Learn, Bug Check 0x124 WHEA_UNCORRECTABLE_ERROR
• Microsoft Learn, Bug Check 0x1C8 MANUALLY_INITIATED_POWER_BUTTON_HOLD
• Microsoft Learn, Memory dump file options (updated February 12, 2026)
• Microsoft Support, Keep your PC up to date with active hours
• Dell Support, Windows Randomly Restarts or Auto Reboots