Are the cooling fans on? If severe enough the fans will be on, if not it may just be a loose connection or a sender is giving a reading which is above or below a threshold.

As said D/C the battery for 10 mins BUT be sure you have the radio code to hand before doing so.

If the light illuminates again it means the fault is still there.

If the fault is bad enough you will know about it as you will be running LOS (Limp home mode) and so will have noticed it on the performance of the car if not it can't be that bad.

Martin