Have a 2006 4.0 with the auto trans at 70K. On the road, the truck shifts well; not Buick smooth, but like other auto cars and trucks that I've driven and I will notice the upshift.

Shifting in and out of any drive gear or Park, I will feel the truck lurch forward moreso than I've had in other autos. I am not sure why this is happening, but I am wondering if this is something I can do to fix it or if there is something I should keep an eye on.

 

Mine does this when the transmission is cold and it gets somewhat better when warm,I have no idea what it is.Maybe someone else will chime in.

 

Reads like a computer problem, even with cold idle of 1,200rpms it should ease into gear not lurch.
There have been quite a few TSB with Ford automatics, if possible have a Dealer run your VIN and see what TSB's come up.
While '06 is well past warranty Ford still pays dealers to fix safety issues and you could just need a software update in the computer

 

had a hard shifting issue with a mercury topaz and that just required a fluid change every 2 years.

 

Had a similar issue, Ford did a software update on my 07 FX4 and that seems to have cleaned things up. Not perfect but much better.