I start my windstar and let it warm up now that it is winter it warms up and on 2002 Ford Windstar

I drive about a mile warm and stop at stop light it starts to cool off then I drive another mile or so and it get warm again the dash says temp says the temp is good do I have a sticky thermostat or bad water pump it don't overheat and no dripping under the vehicle ?

Asked by for the 2002 Ford Windstar
maybe the fan might not be working
no my fan works I just drove it about ten miles with heater on high it gets hot the vehicle don't over heat but when i am at an idle it starts cooling down i put my foot on the acellerator it starts getting warm again
FULL of coolant? Even in the plastic tank!