PC Crashes - Hard Reboot required

[Geissbock_DE]

Bought BF4 two weeks ago, right after I bought my computer and I can't play a complete round...

I join a server, play until mapchange, then I can roughly play for 5 minutes and the PC crashes. Monitor goes on standby but the computer is still running. Can't reboot using the power button, I have to give it a hard reboot. Game works flawlessly until then.

Anyone got an idea?

AMD FX 6300 3.5 GHz

8 GB RAM

GeForce GTX 960

Win7 64bit