Sounds like low tranny fluid level to me.
In 'D', and you drive normally, it should shift 1-2-3-4 at about 2500 rpm each time.
If you put it in '1' when stopped, then go WOT, it should shift up at 4500 each time.
See thread : https://www.crossfireforum.org/forum...dip-stick.html

about a DIY tranny dipstick.

There is an outside chance that the TCM could be faulty.
Raise the car up and check the electrical transmission connector for fluid leaks, quite a common problem on these and MB cars.