My truck has been sitting for theast week at the body shop. I dropped it off with it never having any issues. It's a 2008 sierra with a 5.3. After picking my truck up and leaving the body shop, it suddenly lost oil pressure once it got to normal running temp. I pulled over and checked the oil and it's fine. I towed the truck back to my buddies house and let it sit and cool off. Cranked it back up and once it got to running temp the pressure dropped again and the oil light came on. There's no unusual sounds coming from the motor or anything. Any ideas on what could be going on?