Have you had the fluid changed recently or at all?
The Fluid could be old and its composition might not be lubricating as much as before.
The problem you describe sounds like a fluid problem.
I've had many automatics, and everytime the tranny acted up, it either needed fluid or a fluid change.
Also do you come to a complete stop before you shift to drive, and do you also give it a sec before you hit the gas?
It sounds to me like a transmission slip problem, which is usually fluid related.
Though I have noticed some ford trucks can take 20 seconds to switch from reverse to drive. my car doesn't move more than a few inches when I put it in park on a hill, though if I'm on a hill I always set the parking brake.
If you have no idea when the fluid was last changed, you might want to have it and the filter changed.
Hope that helps.
P.S. I'm not a tech, just another enthusiast who loves all benzes.