The temperature gauge will go to max and then a few minutes later it goes back

Ok. I was told that it was maybe the heater control valve. What do you think about that?

No connection between that valve and the temp gauge!! Thermostat controls engine temp unless there are other issues with the cooling system!! Low coolant, radiator flow problem, head gasket issue... have a mechanic test the cooling system!!

Ok thanks a lot.

You bet...