w124 engine wine on start up (lasts 30 seconds) then fine

[WDB124066]

see the post 7 link
and what to look for
AIR PUMP INTAKE AND EXHAUST MANIFOLDS

Well, above my alternator sits an idler pulley. It's a bit dark to see the others, torch needs new batteries, but if it is supposed to be above the alternator I haven’t got one and my car does this too......

 

[The Boss]

so all in all, its totally normal.. good good!

 

[grober]

Hmm, could someone tell me what's the purpose of the air pump?

It's also known as a "smog pump" its function is to inject extra air into the exhaust to help combust unburnt fuel so its an "emissions thing"
Secondary air injection - Wikipedia, the free encyclopedia

Air pump bearing - PeachParts Mercedes ShopForum

Smog Pump - Benzworld.org - Mercedes-Benz Discussion Forum

 

[WDB124066]

Well, I do believe I don't have one and my car does this just like The Boss's.

Back to the alternator theory, maybe get it tested like Grober said and go from there......

 

[Ian B Walker]

they all make that noise dont they?

mine does too

 

[Ian B Walker]

Hmm, could someone tell me what's the purpose of the air pump?

It pushes air into the cat when the engine is cold. Stops the cat from fouling up.