Originally Posted by Tumbleweed36
First step, try clearing the CMOS if you had a hard shutdown. There are times that the bios gets corrupted with a hard shutdown, so you need to start by trying to make sure the settings are the default.
If you're still having problems pick up an anti-static wristband to ground yourself to the case.
You may want to reseat your processor and apply new thermal paste as this is a common cause of such an issue, however you could potentially damage the CPU in the process. Seek the help of a technician, or a friend that has previous experience performing such an action.
As for your computer restarting rather than shutting down, your problem could either be a corrupt bios of a corrupted operating system.