its probaly your brake light switch on the brake pedal. My accord did that and it was the switch. Check to see if you have brake lights also when your barely press the brake. The car needs to know that you have your foot on the brake to shift from park safely, like kids playing with the shifter when the car is running. My switch was $8 at BapGeon but im not sure about chevrolet switches, advance or autozone should carry them fairly cheap if thats the problem.