One possibility is the engine damper is no longer functional. (Boy, I hope the 240D HAS one!
The damper is basically a shock absorber which is supposed to dampen the rocking motion of the engine. Imagine that
Do a search for "engine damper" as there have been several posts regarding this.
Other posts mention a weak fuel injection rack dampener spring. Search for that also.
'96 E300D 60k mi (wife's daily ride)
'95 Audi 90 120k mi
'92 GMC Suburban 139k mi
'85 300SD 234k mi (my daily ride)