Ok, there is a very common issue on the 3.8L engine which is what is in your GP, which causes overheating and coolant loss without any showing up on the ground underneath it. This is a leaking intake manifold gasket and cracked manifold.
The cooling system needs to be pressure tested and if the pressure drops without any external leak, then the intake manifold and gasket need to be pulled and inspected and replaced if needed. On the low chance it is ok, then the headgasket would need to be replaced. But it is about 90% chance it is the intake.
If the intake and its gasket, it runs around $675 parts and labor to replace it
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