I was sitting in my car in the passenger seat. The car was in Park, engine was idling to warm up the car. No one was in the drivers seat. After about 5 mins, the car started moving forward without me touching or bumping anything. I didn’t notice if the dash display changed from P to D. The shifter light definitely changed out of P. As a result, the car slowly moved forward and bumped a parked vehicle in front of me. No damage to either vehicle due to slow speed. No claim filed. No police report. I just have major safety concerns. I pulled a diagnostic report later and found these codes: SHIFT module codes U0101-00 (lost communication with the transmission computer) and U2141-87