Started accelerating high on highway jerked forward and shut off wont start

Started having issues with it when it went over 30 mph it would accelerate real high sometimes it would stop on its own other times I would have to pull over turn car off wait 30 seconds and it would start with no problem did this everytime I would drive over 30mph. Especially on highway it would jerk forward real hard before accelerating high. Today driving home from work it started accelerating real high after jerking forward hard and the engine cut off on its own and would not restart had to tow it home. Changed the starter its not that brand new battery not that. I don't know if it maybe a sensor the wrench popped up on dash but didn't stay on. Took it to auto zone put tester on it nothing popped up for any issues. What could it possibly be? Help!