If you have any expansion card in the slot nearest the graphics card, this could be affecting the airflow - move it further away. Also make shure that any cable ribbons are tucked well out of the way to improve airflow or, preferably replace with cables.
Now click here
for Asus smart doctor to check exactly what's going on.
You can also add additional cooling - if my memory serves me correctly, this card does not come with a cooling fan.