Video randomly going black

I have an Inspiron 17-7779, from time to time while playing some what graphic intensive games on it will just go black, but the laptop stays on. The remedy I have found for this is tapping the power button on the side, letting it stop running and then tapping it again allowing it to cycle through the lock screen and resume right where I left off without even disconnecting me from the internet. 

what is the world is causing this and how can I prevent it.

Thanks!