Jerky auto

[VUB]

Is this a feature or a problem?

Mustang 5.0 auto.

First scenario. I drive the car, stop at lights but hold car on footbrake. I pull away, nice and smooth and all OK.

Second scenario. I drive the car, stop at lights but put the auto into park. I then put in drive and go to pull away. There is a distinct delay and a jerk as it goes
into first gear. Then off we go!

I have never experienced this on any other auto, so is this normal on a Mustang?

[VUB]

An update ...

.... my car is now in my garage awaiting Ford to phone back. It won't shift past second gear, accompanied with a burning smell.