My car started jerking while stopped (foot on break & in drive) at stop lights. We changed the spark plugs & ignition coils and everything seemed to be running fine for a few weeks. A few days ago, however, my car began jerking again (but a different kind of jerk. Like if someone was pressing on the break & letting go over and over). Also, every once in a while it will die out of no where if I'm in drive and stopped, or if I'm in reverse trying to back out. When it loses power, it will turn back on and rev up, but shuts off as soon as I put it in reverse or drive. Any help would be greatly appreciated!