When I was test driving my car before I bought it from teh ford dealership it was doing the same exact thing, the idle was off when the car was parked somewhere and my parents said that wasnt good.

Another thing was the gas pedal felt extremely hesitant, and it kept getting worse, I would barely push on the gas and the car wouldnt move then id push on it a little more and itd kick up real hard and the car would jump and go. It felt really off.

Took it to the dealership and they replaced the throttle body and cleaned something else out and It runs perfect now.

 

I had the exact same problem you described, and ford replaced my throttle body under warranty and no problems since.

 

I had the same issue it was the TPS. Dealer replaced it and i was good to go.