Computer screen goes black randomly, then performs a startup.

As the title says, sometimes whenever I use my computer, the monitor will go black, and the pc will perform a startup again as if I had turned the pc off and on. I've been trying to troubleshoot for some days now and have still not found the problem. I know temps are not an issue. I have done a full reset of my PC as well. I believe the problem is the ram, cpu, or motherboard. Maybe even the powersupply. In trying my best to narrow down the issues. Any help?

Edit: used different ram sticks. The problem is not the ram.