When I shifted into reverse in a grocery store parking lot, I let the car's natural idle speed take me out of my parking space. However, the car suddenly lunged in reverse as if I had put my foot down on the gas pedal. I had to put my foot on the brake pretty quickly. Luckily, there were no other cars or people around. This is the first time that has happened and not sure what caused it. I drove it home without further incident thus far.