Open Control Panel/Administrative Tools, there open Services, look for the entries Remote Procedure Call (RPC) and Remote Registry, double click the entry and go to the tab named Recovery, it the setting is "Restart the computer", change it to Take No Action, set the three fields like that.

If this doesn't fix your problem, you should check the CPU and power suply fans.

If you suspect a trojan or adware infected your computer, I will also recommend you to go to PC Tools - Essential tools for your PC and download PCDoctor, you can fix your computer with the trial.

System Restore can be effective, but if you are restoring from a point where the computer was already infected you will eventually experience the same thing.

Good luck!