It all started with a clonk when starting from stand still. I search the web and didn't find much - so I thought I add to the shared knowledge.
Note: I'm not a trained MB mechanic and you may not want to do what I did. (I did a similar procedure on my Jeep Wrangler when adding motor mount lifts, but that was very straight forward - lots of room.)

Problem:
Car would make a clonk when starting a forward direction. Being very light on the skinny helped and pushing hard made it lauder. First I thought it was a U-joint or transmission part.

Car: ML430, 90k miles, 2001

Diagnose:
Standing on the break and doing the same thing, still gave the noise - opening the hood showed the engine moving/lifting with the torque - Bad motor mount on drivers side.

How-To:
The local dealer wanted $800+, so I started searching for How-To's. Didn't find much, more than - strip the engine - lift it (out?)...Didn't want that.
Mounts was $44 at the dealer, the transmission mount ca $80.

The drivers side mount is really hidden behind AC-pump, Power-steering, front-diff, exhaust, drive shafts, axle - you name it - it's all there

First I put the car on jack-stands, holding the frame behind the wheels. I removed the plastic engine shield on top and the splash guard underneath. This gave access to the two lower bolts that held the fan shroud - which was loosened.

On driver's side, I removed:
- inner plastic fender (wheel housing liner) - easy
- heat shields behind the fender - messy, two bolts from the front and one from the rear. The rear bolt was a PIA to reach with large hands.
- this gave access to the motor mounts upper bolt from the side.
- the two lower mount bolts was reachable from below, although one was just behind the drive shaft and was another PIA.
- I later also took of the wheel to get better access.

Passenger side was easy: Pull out the airbox - unsnap lid, and inlet from MAF, lift out box. This gave access to the upper bolt and the lower bolts was in open sight from below.

Next step - get the mounts out. I used my garage jack with a wood piece that fit between the cross member and the sway bar. I added another piece to spread the load and then lifted carefully until the car started to follow.
- Passenger side mount came right out.
- Driver side was broken = top part not attached to the rubber. This made it a little larger, so after replacing the passenger side mount, I lowered the engine and moved my lift point to the driver side. With an addition of a gorilla bar, i did get the drivers side out and the new one in.
- To get more play, I also loosened the transmission mount and its cross-member.
Note: putting your hands under any part of the engine when lifted by the jack is not safe.

Put all parts together and no more clunk.

How long: - It felt like forever, but probably some 6+ hours, including searching for dropped bolts and figuring out the next step. Next time would be much faster. Not sure that an engine hoist would help much.

Pic1: Engine jacked up
Pic2: Drivers side motor mount seen from wheel well.

Hop this helps someone.
Cheers

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thats pretty much the way to do it. only difference when I do them on the V8's I position the jack more toward the side I'm doing at the time.

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1980 500SE/AMG Euro
1981 500SEL Euro
1982 380SEL
1983 300TD
1983 500SEC/AMG Euro
1984 500SEC
1984 300TD Euro
1986 190E 2.3-16
1986 190E 2.3
1987 300D
1997 C36 AMG
2003 C320T 4matic

past: 1969 280SE 4.5 | 1978 240D | 1978 300D | 1981 300SD | 1981 300SD | 1982 300CD | 1983 300CD | 1983 300SD | 1983 380SEC | 1984 300D | 1984 300D | 1984 300TD | 1984 500SEL | 1984 300SD | 1985 300D | 1986 300E | 1986 560SEL | 1986 560SEL/Carat | 1987 560SEC | 1991 300D 2.5 | 2006 R350

Your description fits what I am facing. Thought it was a CV joint problem. Appreciate the time you took to post this.