Recently I have my PC components into a brand new PC case and for the little while it was working well with no problems at all. But then about a day later I'm getting instances of my PC shutting down randomly, and when I say shutdown, it just stops, before of course tarting right back up again. It occurs most frequently during startup and less frequently when it's actually managed to start up windows. Some cases it'll just start for literally a second and stop.
Temperature wise everything is fine. I have a water cooler keeping my CPU at around 21 and the fans always come on when it starts up. Same with the GPU, using a water cooler and keeping everything well below average temp. At this stage I'm going to go with the PSU acting up, but I don't want to rule out other possibilities as well.