I have a Gigabyte r9 280x and I have been having this issue for awhile, its intermittent and doesn't do it in all games but most of them. I have never overclocked the card, my frame rates are always great, and changing in game settings and trying new drivers haven't helped. The card has done it since it was new and the only reason I did not RMA it was because it was a gift and I have no idea where they got it. Here is a picture of what I am experiencing, When it does happen usually restarting the game or my entire pc fixes it and it goes away until another random point in time,