The contact owns a 2019 Chevrolet Blazer. The contact stated while driving at various speeds, the vehicle accelerated and decelerated independently. The contact stated that the message to ‘Shift to Park’ was displayed while shifted to park(P). The vehicle was taken to a local dealer and the contact was informed that the gear shifter needed to be replaced. The vehicle was repaired; however, the failure reoccurred. The vehicle was taken back to the local dealer; however, the failure was not duplicated. The vehicle was repaired. The manufacturer was not made aware of the failure. The failure mileage was approximately 61,000.