My iPhone restarts everytime is heating up

Hey, i had a problem, my white iphone 4S restarts eveytime i use facebook for more than 10 minutes, or i play a game(e.g. Temple Run) for more than 10 min.

So when it's heating up, i feel that is very hot then, Bang! my display becomes more pixelate, and it restarts

Also, my camera doesn't work for several months, when i try to enter Camera, it restarts

I`ve put a youtube video below so you can see. Anyway, i bought a camera to replace it an tomorrow should arrive. i`ll keep in touch with updates .... but meanwhile, anybody has some ideas why my iPhone restarts over and over again?

http://youtu.be/1Bs0K3FO_0k