Yep that sounds like an overheating issues, listen to onpon4 :).
I used to get this on my desktop every once in a while, after a few months of the exact same symptoms I investigated, I found that not only was the CPU fan dead but the heat sink wasn't even attached any more!
If the cooling solutions mentioned above don't work, you can always try under-clocking the components via the firmware this will at least give it a little more stability provided you don't mind the performance drop.
