2006 Mercedes Benz 350sl noise

I believe the sound you are hearing he is a climate controlled circulation fan which is probably located by the shifter on the center console

Good call, I have seen the blower motor make all kinds of strange noises, here is the location so you can unplug it to see if the noise goes away, and if so this is how to replace the blower motor as well. Check out the images (below). Please upload pictures or videos in your response of any problems so we can see what to help you with.