Disable automatic restart on failure
Right-click This PC → Properties → Advanced System Settings → Startup and Recovery → uncheck "Automatically restart". This lets you read the BSOD stop code instead of rebooting instantly.
Check temperatures
Install HWMonitor and watch CPU/GPU temps under load. Thermal shutdown occurs without warning — if temps hit 100°C, overheating is the cause.
Test the PSU
Restarts under load (gaming, rendering) with no BSOD often point to a PSU unable to deliver sufficient wattage. Test with a PSU tester or try a known-good unit.
Run MemTest86
Random restarts without BSOD or thermals issue are classic bad RAM behaviour. Run MemTest86 for 4+ hours.
Check Windows Event Viewer
Event Viewer → Windows Logs → System. Look for Critical events just before each restart. Kernel-Power Event ID 41 means unexpected power loss — points to PSU or power delivery.