Laptop shutting down

[Moutaz]

My laptop (Lenovo Z510) keeps shutting off by itself every once in a while for no apparent reason and without a warning, it's not overheating.. it just shuts off whenever I'm gaming and this problem has been only happening recently.
need help please :/

 

[Moutaz]

The temperature of cores is usually 55-60 during gaming and GPU is 60-70