What could be wrong with my 2005 Monte Carlo car?

What is your question?

The temperature gage will run kind of hot and I can stop the car and turn the keys back and bring the gage back down to C and turn the car back on and it isn't hot and their isn't any symptoms of my car overheating but the gage doing this what could be the problem

How long has your 2005 Chevrolet Monte Carlo had this problem?

A month or so