This sounds more like weak or worn springs...I am assuming they are original?
The symptoms you describe are caused by a suspension that feels as if it's "floating" rather than "tracking"
Generally MB springs don't call themselves to attention unless they are extremely old. So check struts as well...
2009 ML350 (84K) - Family vehicle
2001 CLK430 Cabriolet (71K) - Wife's car
2005 BMW 645CI (124K) - My daily driver
2012 Mustang V6 (60K) - Daughter's car