PC black screen and restarts when launching games

This is an issue that I have been having for quite a while now (around 1 and a half to 2 years). It is weird because it is inconsistent and sometimes seems to fix itself. What happens is that I try to launch a game (even ones that my pc has better than recommended specs) and on a screen that says 'click to continue' or Main Menu, the PC black screens and restarts. I have sometimes fixed the issue by factory reseting the pc, which is what I did the first time, but that has not helped since. It recently happened around the 5 of January. I tried factory reseting and checking for viruses, as well as making sure all cables are connected correctly and thermal paste is there, but it still didn't work. I eventually just left it for a couple games where I didn't play any games, and it fixed itself around the 15th of January. It has now come back and so I am on here trying to see if anyone has any idea of what it may be.