You can try to see if Event Log tells something that points to a possible cause.
- If yes, see if fixing that cause fixes that problem.
- If not, go back to factory conditions.

- If it's fine in factory conditions, gradually go forward again to your current state. It's a good idea to make an image backup once in a while so you can go back to the latest good situation if it's caused by some software you install.
- If it still happens, most likely it's a hardware issue. Then have it repaired.