I have had alot of experience with this subject and there are only a few things that can cause this.
1. If the poly-belt tensioner is the least bit loose and allows any slip, the compressor will cycle off until restart.
2. If the compressor relay is defective it can cause this. It isn't a pushbutton unit problem if it cycles OK.
3. The sensor in the rear of the compressor can go bad only above a certain RPM. It sould generate an AC sine wave at all RPMs going up in voltage as the RPM's increase.

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Benzmac:
ASE CERTIFIED MASTER AUTO TECHNICIAN
LEAD TECHNICIAN FOR 14 BAY FACILITY
MERCEDES SPECIALIST 8 YRS
PARTNER IN MERCEDESSHOP.COM