I have a 1992 300E with the 2.6 motor. It's been running great since I got it, but then tonight as I got home it started acting up. As I'm driving through my apartment complex I hear a noise like a firecracker going off in the distance. Once I turned down my music and rolled down my windows I hear a sound like belts squealing. That went away after about 10 seconds and then it turned to a noise like putting cards in the spokes of a bicycle as I continued down the street. I parked it, turned it off, and restarted it, and the noise continued. It's not super loud, but gets a bit louder as the RPM's increase.

Any ideas? Thanks for the help.