On a trip to Texas in my husband's 2005 roadster, the car started making a noise (seemed to come from underneath center console) that sounded EXACTLY like the bicycles with a playing card attached to hit the spokes when I was young.
I didn't find anything here and wouldn't have thought to look at Benzworld where my husband found someone's post describing it this way also.
It turned out to be a very minor issue involving insulation around the drive shaft.
I don't know how hard it is to get to because for me, it suddenly stopped on it's own, but I wanted to help others avoid the dreaded thoughts of what could be wrong.
https://www.benzworld.org/threads/strange-noise-like-the-old-card-in-the-bicycle-spokes-sound.1302319/

 

I had a similar noise when I bought my car but was easy to diagnose. It was beneath glove box and would vary with fan speed. The interior fan motor had a small but very tough maple key wedged at the bottom just like a card on bicycle spokes.. It was stuck in there a lot better than any card I have ever attached to a bicycle. Easy fix.

 

Had the exact same problem in my car. Was leaves that got into the blower fan..