1996 lurching forward with brake on

This problem started a few months ago. First it happened when I put the car in reverse, while my foot is still on the brake, it would jerk and seemed to be revving up the motor and trying to move in reverse with my foot on the brake. Now it is doing it when I change gears into drive with my foot on the brake it seems to try and lurch forward in fast speed while my foot is still on the brake. I keep my foot on the break while this is happening because it seems the car is in full throttle and would just jerk forward at high speed if I let off the brake. After a while it will jerk back into a normal throttle or the engine will die and I have to restart it. Sometimes grayish smoke will appear during the high throttle phase. It scares me. It feels like I'm trying to hold back the car from taking off on it's own.