Quite normal (at least for the M104). Age-related issues magnify the noises (dried belts, seals etc.).

Mine is normally smooth, but on occasion I've experienced rough idle at startup...even if only sitting for a few days.

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2009 ML350 (106K) - Family vehicle
2001 CLK430 Cabriolet (80K) - Wife's car
2005 BMW 645CI (138K) - My daily driver
2016 Mustang (32K) - Daughter's car