While driving my volvo c30 redesign, i stopped at a stop sign before i entered main road from parking lot area vehicle began to accelerate to a high speed independently causing the car to move towards the intersection. no cars were approaching so i continued turning but it was very unsafe. it happened before at fort hood and near my house in temple tx. always same conditions; as i start to accelerate the vehicle jump into a high speed or gear. this morning the vehicle was on high rev idle, did not went down until i change to manual and back to automatic. please advice. *tr