You haven't left us much info here. Fill in some of this info i putted below, then it would be much easier for anyone to find your card's problem.
Do you have a small case?
high room temp when gaming?
Are you using Mantle or DX11 in BF4, try using the one you don't use?
Have you tried any other games or is it only in BF4?
Have you playerd BF4 before without problems?
Though my solution without any info would be that you should just try sending it back for repair/replacement.