PC restarts, shuts off or freezes randomly
Find out whether it was a hidden blue screen, a power problem or a hardware fault.
A PC that restarts, switches off or freezes on its own usually falls into one of three cases. Windows hit a blue screen and restarted before you could read it. The PC lost power, for example because of the power supply or overheating. Or the hardware stopped responding, so you had to hold the power button.
Microsoft notes that a single unexpected restart is often resolved by the restart itself. When it keeps happening, the clues below tell you which case you have.
How to tell which case you have
- After the restart, open Event Viewer (Win + R, eventvwr.msc) > Windows Logs > System and find the Kernel-Power event 41. On the Details tab, a BugcheckCode other than 0 means a hidden blue screen.
- If BugcheckCode is 0 and PowerButtonTimestamp is not 0, the power button was held down. If both are 0, Microsoft says this typically indicates a hardware problem, such as power loss.
- When the PC freezes, press Caps Lock. Microsoft uses this test: if the light does not change, the whole PC has stopped responding, not just one program.
- To see the stop code next time, turn off automatic restart: Win + R, sysdm.cpl > Advanced > Startup and Recovery > Settings > clear Automatically restart.
Start here: read the restart event
This guide explains the Kernel-Power 41 event in detail and turns its codes into the next step.
Hidden blue screens behind random restarts
These stop codes are common when a PC seems to restart for no reason, especially under load.
WHEA_UNCORRECTABLE_ERROR
Windows stopped because a piece of hardware reported an error that could not be corrected. WHEA (Windows Hardware Error Architecture) is the part of Windows that collects these reports, so the stop code says who…
ProcessorMACHINE_CHECK_EXCEPTION
The processor detected a hardware error it could not correct and stopped Windows to prevent data corruption. On current Windows versions the same event usually appears as WHEA_UNCORRECTABLE_ERROR (0x124); the older…
ProcessorCLOCK_WATCHDOG_TIMEOUT
Windows stopped because one of the processor's cores did not respond to a regular clock signal in time. Microsoft explains that the core is usually unresponsive or deadlocked.
GraphicsVIDEO_TDR_FAILURE
Windows tried to recover an unresponsive graphics driver, but the recovery failed.
MemoryMEMORY_MANAGEMENT
Windows stopped because it found a severe error in how memory is managed, such as damaged page tables or memory records that no longer match. Microsoft describes several of its specific error types as probably…
Freezes and hangs
The PC stops responding for a while or completely. Drivers that stall and storage that resets are common causes.
DPC_WATCHDOG_VIOLATION
Windows stopped because a driver held the processor for too long. Drivers handle hardware events in short, high-priority routines (deferred procedure calls, DPCs), and a watchdog in Windows triggers this stop code…
StorageNVME-CONTROLLER-RESET
Windows sent a command to the NVMe SSD, got no answer in time and reset the drive's controller. Event Viewer records this as Event ID 129 from stornvme with the message "Reset to device, \Device\RaidPort0, was issued".
MemoryMEMTEST-ERR-8
A memory test such as MemTest86 or Windows Memory Diagnostic reported errors: data written to RAM did not read back correctly. Errors like this can cause crashes, blue screens and corrupted files.
First steps for random restarts and freezes
These checks come from Microsoft's articles on unexpected restarts and Event ID 41. Do them in order and use the PC normally for a while after each.
- Remove hardware you added recently and check Device Manager for devices with a warning sign; update or disable them.
- Install the latest Windows updates and the current drivers for chipset, graphics and storage.
- Turn off overclocking, including XMP or EXPO memory profiles, and check CPU and GPU temperatures.
- Run Windows Memory Diagnostic (mdsched.exe) to test the RAM.
- Check that the power supply is strong enough for your components, and plug the PC straight into a wall socket.
- Keep 10% to 15% of the system drive free.
- If it started recently, use System Restore to go back to a point from before the problem.
Sources
- Microsoft Learn: Event ID 41 "The system has rebooted without cleanly shutting down first"
- Microsoft Support: Troubleshooting Windows unexpected restarts and stop code errors
Written and reviewed by Matyáš Rada.