Nope not normal but should be easy fix.
1. Clunk means loose vacuum hose on the tranny... One the driver side of the
tranny... by a round device there is a vacuum hose... most of the time, the
hose deteriorated and is very loose. Change it with MB vacuum hose 1.5"
length. but get a foot for spare.
If the vacuum hose is tight, then you have to adjust the modulator... BUT
higher engine idle RPM can do the same clunk.
2. Engine should idle at 800 when not in gear. In a gear, it should idle at
500-600. If not, then it is most likely the idle control unit that is bad...
get it from Automotive Technical Service... look for the info at
mbcoupes.com under part supplier.
There is a procedure to test the entire circuit with a multimeter...
measuring voltage and resistance to determine which one is at fault before
you replace it... you can get that info in a MB service manual CD.