PC keeps shutting down randomly

I've been having this annoying issue ever since I updated my PC. So, I set it up so the monitor turns off after 5 minutes and the computer goes into sleep mode after 10, but basically, the screen just goes black while the tower keeps running away. Is there a way to fix this, or is it obviously some kind of bug?

My PC just randomly wakes itself up too, and I can't figure out why. This is what shows up in the Event Viewer:

The system has exited sleep mode.

Idle Time: ‎2016‎-‎01‎-‎16T20:11:05.175574100Z
Wake Time: ‎2016‎-‎01‎-‎17T02:29:43.224866900Z

Wake Source: Unknown

Done and dusted