Computer randomly black screens

[bwinzey]

So I just finished building a new computer, and sometimes while playing a game (Rainbow Six Siege), Both of my screens go black, and don't change until I manually reboot the computer. If I let it sit there, it goes into what seems like the default windows 10 desktop, and all I need to do is sign out of that and sign back in and the computer works fine.
Specs:
OS: Windows 10
HDD: 4 250 GB Hard Drives (RAID 5)
Motherboard: Intel S2600COE
Processors: 2x Xeon E5-2670
PSU: Corsair 750W
Graphics card: PowerColor DEVIL R9 390x
RAM: 32GB (4x8GB) Samsung 2Rx4 PC3L-10600R M393B1K70CH0-YH9

Anyone experienced this before? Should I try to reinstall my graphics card drivers?

 

[Colif]

Have you got win 10 set to auto logon? might want to remove it as it could be why you get the default logon sometimes, I had similar problem on my PC where it refused to logo me in at start and logging out was only way to fix it. It sounds like it logs you into a guest account.

What model power supply is it? could be you run out of power for gpu while playing and it turns screens off