|Can sometimes be a RAM problem. If you can get to the sticks, clean their edge connectors with a pencil eraser then pop them in and out a few times to clear oxide of the sockets too.|
If you have more than one stick then try them one at a time, or you can download a memory test.
Of-course it might not be RAM but that is a common cause of this symptom.
Always pop back and let us know the outcome - thanks