Coolant monitor

So when i start the truck 1st thing in the morning, especially in the winter time, my temperature gadget goes through the roof!
Yet…it’s not actually over heating, fluid is good.
After i drive it about 20/30 miles down the highway, it drops down to half way.
I’ve changed the thermostat twice, so what else could it be??
TIA for all the helpful replies :slight_smile:

Trapped air in the cooling system or a faulty temp sensor.

I would try replacing the coolant temp sensor.