Monitors Turn off, Fans go on full power when playing games.

As the title states, when I am playing games, both monitors will turn off and the fans on my PC go on full power. The PC is still responding as I can hear my character react when I use the keyboard. However, the screens stay off and I am unable to turn them back on - the only way to fix it is to restart the PC using the case power button. This has only started to happen recently, I have not downloaded anything new or added any hardware - I have never experienced this before, my PC has ran fine since it was built in late 2013. I have uninstalled the games and downloaded them again and I clean my PC regularly. Any advice on what is causing this issue would be appreciated.

System Specs:

• CPU -Intel i5-4670K,

• CPU Cooler - NZXT KRAKEN X60,

• GPU - MSI Nvidia GeForce GTX 780,

• SSD - Samsung 840 EVO 120GB,

• HDD - WD Black 1TB,

• PSU - Corsair RM Series RM 750,

• RAM - Corsair Vengeance 8GB,

• Monitor - BenQ XL2411T (x2)

• OS - Windows 10