Computer Suddenly Restarts

My computer suddenly restarts on it's own. I've cleaned it, checked for loose connections. The temps are fine (for where I'm from anyway, pretty hot here most of the time). The time between restarts shortens through continuous usage. My computer's always having problems (replaced the psu due to it getting grounded, reformatted multiple times to fix software issues). This is the first computer I've built by the way. This started after installing a game but I already uninstalled that. And the errors I get from event log are normal (from what I've gathered from other threads). I tried checking my memsticks yung memtest but it still restarts on it's own. As I've said, my psu was recently replaced (less than 6 months ago).