Possible reasons could be,
- PC being overheated.
- Dust having being accumulated all around.
- CPU fans not working properly .
- Faulty power connections.
- Faulty circuit board from where the power is being drawn.
- Support Drivers not having being installed.
Debugging steps which can be taken are:
- Cleaning the system thoroughly and maintaining it in a dust-free environment.
Environment that is cool enough and facilitates for easy passage of air should be ideal enough.
- By locating the appropriate support drivers for the system in consideration and having them installed.