Game freezes

For some reason whenever i start my game up after a few seconds the game freezes and the only way for it go back to normal is alt-tabbing, but even then it freezes after a couple seconds. The weird thing is that this only happens for about two weeks, goes back to normal for about a week, then starts crashing again for another two weeks. Any ideas as to what could be happening?

Its a lenovo y580 laptop

3rd Generation Intel® Core™ i7-3630QM (2.40GHz 6MB Cache)
6GB (DDR3)
NVIDIA® GeForce® GTX660M 2GB with DirectX® 11
Windows 8 64