Your fans are most likely to blame. If they're not spinning correctly, then your computer will overheat. Since you haven't had it more than a year, I'm guessing it's still under warrantee. Talk to whoever you bought it from, and they should fix it for you.
edit: this also might happen if you block your fan intake ports. A simple solution if that's happening is to raise the notebook an inch or two off the table or whatever you're using it on.