1994 4runner automatic 3.0 overhat problem

What is your question?

run at normal speeds it will stays cool just in the center of the gauge. stop and turn it off let it sit for a few mins. and restart and if will get hot drive down the road or sit and rev it up and will cool down. Coolant level is good fan is good fan clutch good and no leaks from the water pump. It will fill up the over flow and loss of some coolant so I think water pump is working. could it be the thermostat sticking? will not overheat after I get it to cool down. also the radiator was replaced 2 years ago. thanks for your help