last night i went to the gas station and parked my car. got back in it and when i started it it was very rough. then my airbag light came on and my emergency brake light would not go off when the brake was off. also my check engine light was on and has been since i bought it (got it checked out and nothing major: missfire in cylinder 3 and a small evap leak. i also just got new brakes about 5 weeks ago). I then put my car in reverse to see if it would fix the problem and then put it back in park. when i put it in park it made a awful loud grinding noise...i turned the car off waited and tried again and it did the same. waited again and this time it was perfectly fine. i drove it today with no problem. anyone have any ideas what the problem could be? any help would be greatly appreciated.