It sounds like it is falling apart.
I have a 2000 GM Silouette.
Less things have gone wrong with it than your Mercedes.
(70,000 miles)
I never thought GM would build a more reliable car/truck than Mercedes.

But when it comes to driving it.. the slush bucket van cant compare to my tight near 100,000 mile ML320.

__________________
Steve Danville
what i did myself.
CPS
rear shocks
MAS x 3.
SparkPlugs (twice)
Fuel pump & Filter
Window switch
replaced both failed horns with Honda horns.
Cleaned ERG Tube
Oil changes
Oil consumption Fix
Brake Pads
A/C Recharge
Anti-Freeze change X 2.
Front Shocks. Monroe. $90
Mercedes Warrenty Work:
Harmonic balancer,power steering clamp. Cat converters.Drive Shaft Bearing.s
Replaced Outer Lower Tie Rods and front lower ball joints at 156,000 miles