I have the same issues as noted in the original post. My 99 E320 4 matic has 100k miles on it. I just had it at the MB Specialty shop to have the transmission serviced, oil and filters changed. Used Mobil 1 Full Synthetic.
When the weather is around freezing and the car has not run for more than 6 hours the transmission does not engage. The engine will rev and in a few seconds the transmission engages with a bang. Then it takes a couple of minutes of driving in first gear revving between 3 & 4k rpm before it will up shift.
The shop is talking about a rebuilt tranny but I have to believe that there is a simpler more financially viable option. Can anyone provide some advice for a solution.

thank
Kechika