My 318is does the same thing. It's an auto and it has severe "engine braking" as I like to call it. I'll be going 95mph and let of the gas: it jerks but the tranny doesn't shift down or up and in a couple seconds I'll be doing 80mph. I don't think that anything's wrong with your car, it's just the quick switch between depressing the gas and letting it go that makes the car jerk a bit. It's nothing to worry about. Peace.