This last week my PC has started randomly restarting. Didn't seem to be any consistency to it, just would happen randomly. I thought it might have had something to do with Windows 10, but all I could gather from the error report was that power was lost unexpectedly. So I tried just booting into the Bios and leaving it to see if it happened there, and it did, twice. So I'm pretty sure that would make it not related to Windows 10. I've used one of those PSU calculators and it seemed to come in about half of the PSUs rating. The PSU though is about 7- 8 years old now though. I recently rebuilt my PC with new parts but left the old PSU in as it seemed to be ok.
Is there some other basic trouble shooting I can do? I plan on opening it up over the weekend, and cleaning out any dust and checking connections etc.