Your seat weight sensor is probably broken. It happened to me. You can check it easily a few way. The car should not go into park if your in the seat with the door closed and no belt on. If it doesn't detect you in the seat it throws itself into park over and over when your belt is off.
1. Sit in your can open and close your door with the driver's seat belt off and not touching anything. If your screen turned off it's because the seat sensor is not picking you up.
2. Unbuckle your seatbelt while parked. Do you see a seatbelt warning icon? If it's not there the car doesn't think anyone is in the seat. The seatbelt icon should be on whenever you are sitting down without a seatbelt on. If you lift your body off the seat the icon should disappear.
