Q: Car Kind of jolts or jerks right when coming to a complete stop.

My car jerks/jolts before coming to s compete stop. It can be harder or softer depending on how I break, but if I slam on the brakes, the car will stop perfectly without making the jerk/jolt. I've had a mechanic say it's the brakes friction. I thinking it's the transmission. Also when I'm a complete stop and accelerate with a heavy foot on the gas, when the car is going from 1st to 2nd at about 2000 rpm the car also jerks, then shifts normally. Sometimes when I drive in traffic it gets worse, it does the jerk thing when I start braking and comping to a stop. Thank you. My car is an automatic

My car has 107224 miles.