Cooling Problem
 

Started my 2000 s4 today and the temp gauge started at the half point. And as it warmed up it went to saying it was hot. I checked the water and it's all there and the motor did not seem hot. So is it the sending unit or the thermostat? Help would be great. Thanks.

its probably the coolant temp sensor.. if your veh is not overheating

just a week ago my temp gauge is also acting kinda goofy except it shows it is not warming up at all and cel came on - havent scan for code yet but
my money is on coolant temp sensor..