do some self checks before you RMA your graphics card.
-check for loose cables(notably the "data" cable running from your pc to your monitor)
Push it in properly/harder
Turn of PC before you do these:
-Resit your graphics card properly(might as well clean the pins with IP-Alcohol)
-Resit RAM
-Check PSU Power cables to your graphics card
But chances are your graphic card has problems but better to do these than go all the way down to RMA and find out its fine.
It's also worth noting that you are running a low end PSU that is 620W for a 980ti. In other words, they may be not enough power or your PSU is struggling to give proper power to your GPU.
see source:
http://www.realhardtechx.com/index_archivos/Page362.htm
Even though it says 600w is recommended, you still using a low end psu. It might be one of the problem since it only happens in game(heavy load on gpu)