This sort of symptom is often caused by component (CPU and/or memory) overheating. Make sure the system is clean of dust, and that all the fans are working properly.
rubberman
Posting Maven
2,571 posts since Mar 2010
Reputation Points: 365
Solved Threads: 305
Skill Endorsements: 51
What is the make+model of your computer? We need to see if you can get a hardware diagnostic program for it. A lot of manufacturers, such as HP, Dell, etc. have them that you can download and run from CD, floppy, USB thumb drive, etc.
rubberman
Posting Maven
2,571 posts since Mar 2010
Reputation Points: 365
Solved Threads: 305
Skill Endorsements: 51