Humming noise at start-up

[Spencer A]

I recently bought a '95 E320 Special Editon sedan,(3.2L/44K miles), and had the serpentine belt replaced at AutolabUSA. Since then I have noticed a sort of "humming" sound coming from under the hood when I first start the engine which gradually subsides within approx. 1 min. Any suggestions as to whether is is related to the new belt. Also, to anyone lives in the Detroit metro area; can you recommend maintenance/repair facilities in the area that you trust and are reasonable when it comes to regular maintenance and repairs. This is the first MB I have owned. Appreciate all responses.