2nd source or used shocks
 

Well the TE is vibrating like a harley and swaying side to side like a beat up horse. The mech at the MB dealer "thinks" the rear shocks are gone. but I have the following questions.

He said the pump is working and everything is alright up to the shocks.

The car is visibly going side to side at slow speed and the when you push on the rear bumper it feels firm (normal).

If it is the shocks is there a 2nd source available?

Sounds like one of the rear suspension arms more than shocks.

Shock have nothing to do with side to side motion.
Shocks operate up/down.
If you have excessive side to side motion, suspension arms/bushings are the culprits.
JackD