I was parked getting ready to back up. all of a sudden my engine revved up and the rpm kept climbing and going up and down. I shut the car off. restarted the car and it did it again, I then shut it off took key out of ignition and restarted it again after 5 min.

the little wrench light came on during this process but once I started it again the light went off and it was back to normal. I'm really scared this will happen as I'm driving and I wont be able to stop it..