Why doesn't Dante play? Who is Mrbeck?

I've had the same problem, it turned out my gpu temperature became too high after playing for a while. In overwatch options you can enable an option that shows your current gpu temperature while playing. Mine went up to about 90 degrees before shutting off. You could try to remove all the dust accumulation out of your computer. But im playing on a laptop and didnt want to open it up, so i downgraded my maximum processor status to 75% in the energy settings, that fixed the problem for me!