PC randomly restarts itself. (Windows 10)

[Mymar]

I'm at a total loss here, everything I've found  doesn't seem to be the right fix.  My PC will restart at least 2, sometimes 3 or 4 times a day, it acts like a power thing, but I don't think it's a power thing. I'm getting no error messages or anything, and I'm at a total loss. It seems to be specific times almost, but I haven't payed close enough attention to when the computer actually shuts down. So any thoughts on what it might be? It's a home built system, that's normally pretty good except for lately.

[Vekseid]

Often this is temperature related. Do you have a cpu temperature monitoring program?

[Mymar]

Could it be a loose connection? For instance could it be the power chord, or  maybe something else connected to  the power supply? Mine is fully modular.