rear suspension goes down after sitting for a few hours and goes up after I star

Leak check the bags and lines between pump and shocks.

These cars are notorious for leakage in the air ride system. My compressor ran so much it finally failed. You can have a mod kit installed. They put in new springs and shocks. Not expensive at all. Fixing leaky air bags and a bad compressor is. Honestly, I can't tell the difference since they were installed.