what tv show had a doctor who live in an rv in the parking lot

The show you’re probably thinking of is Trapper John, M.D. The doctor was Dr. George “Gonzo” Gates, and he lived in a motorhome/RV in the hospital parking lot.

A couple of other details point to the same show:

• It was a medical drama from the late 1970s and 1980s.

• The RV-in-the-parking-lot detail is explicitly associated with Gonzo Gates.

If you were thinking of a different doctor-in-an-RV character, that’s the strongest match from the available results.