Laptop shuts down while playing games on normal temperature.

Hey guys I have a Intel(R) Core i7-2630QM with 2.00 ghz and display driver is Nvidia geforce Gt 525m 2gb virtual memory and 6gb ram.

Whenever I play a heavy game like Farcry 3 or Crysis 3 my Laptop shutsdown after a few minutes. I have this laptop for about 2 years but then there was no sign of this problem. The temperature is normal (eventhough it gets hot but still earlier my laptop had been way hotter and it did'nt shut down.)

I am also confident that there's no dust trapped. This only started when I started playing Crysis 3. I am clueless. This problem is getting worse. HELP!