My PC is randomly restarting with no blue screen and no error log. Where do I even start diagnosing this

[StringTheory83]

Q: Random restarts, no BSOD, no Windows event log error at the time of the crash. The machine just reboots as if someone hit the reset button. Happened three times this week, once under load and twice at idle. Where do I start?

Running Windows 11, custom build, about two years old

[Phil80]

No BSOD means Windows did not have time to write a crash dump, which almost always points to a hardware problem rather than a software one. The OS is not crashing, the power is just cutting

[Midnight Georgia]

First suspect is the PSU. A failing power supply under fluctuating load is the most common cause of instant-reset no-BSOD shutdowns. Run a PSU tester or swap it with a known good one if you have access

[StringTheory51]

Spot on. Nice one.

Disk health is worth running a diagnostic on before spending on anything

[ProperJobs]

Check your temperatures under load first before anything else. Download HWInfo64 and watch CPU and GPU temps while running something demanding. Thermal shutdown can look exactly like a random restart

[Dark Hawk]

Also check the CPU power connector on the motherboard. A loose 8-pin EPS connector can cause instability under load that presents exactly like this

[Finley]

RAM is the other big suspect. Run MemTest86 from a USB drive overnight. Bad RAM causes random crashes that sometimes do not generate useful error logs

[Cass_9]

Check Event Viewer under Windows Logs, System, and look for entries just before the restart time. Filter for critical and error. Even if the crash itself is not logged the events in the seconds before often point at the cause

[CollapseState]

Two years old means the thermal paste on the CPU may be degrading. Not the most likely cause but worth adding to the list if the other checks come back clean

[ArmandoCardoso]

Is the reset happening more when the GPU is under load specifically. A failing GPU can pull enough power to destabilise the whole system even when the PSU is technically adequate on paper

[Jason99]

Reseat everything. RAM sticks, GPU, all power connectors. Two years of thermal cycling can loosen connections enough to cause intermittent contact issues that are impossible to diagnose remotely