If it's not the power options then it could be a lot of things...
Can you give some more details:
When does this happens and what you are doing when this happens? (is it after 8 hours of gaming, or 10 minutes of youtube, or after you leave the computer idle for 5 hours, etc)
When did the problem start occurring? (since you got the computer a year ago, or last week after you lost power, or after a software or driver update, etc)
Any other helpful information or observations?