Got a PC that’s a hodgepodge build of components from a few different upgrades over the last several years. It’s been pretty stable throughout that span, after I replaced a flaky power supply a couple of years ago. However, for the last couple of weeks I’ve had a recurring reboot issue.
Seemingly out of the blue, about once per day, while idling, the PC reboots itself and lands back on the login screen. There’s no instigating events I can find in Windows Event Viewer; just a “unexpected power off just occurred” complaint from after it’s done rebooting. In one instance, the PC died while it was processing some TRIM operations on hard drives late at night, but it hasn’t been doing that during the others as far as I can tell.
It only ever happens when the PC has been left idle for long enough for the monitors to go off – never during use, including during heavy use when I was streaming some games at 1440p awhile back. That usually translates to “after I go to bed, between 2 and 9 AM,” but it rebooted while I was taking a midday nap today, for instance, so, no real consistency there.
There haven’t been any major hardware changes leading up to these reboots, nor any major software changes that I’m aware of.
How the heck do I diagnose a thing that isn’t leave traces of its cause?