I did have the same problem with the steering noise. It was a squeak noise coming from the steering column. At the beginning, the noise would go away after the car had warmed up. As the problem progressed, the noise got louder even the car had warmed up.
I went to the dealer. I was trying to play "DUMB" and said the noise was coming from the air bag. The service advisor immediately knew it was the steering boot problem. The technican put some lubrication and the problem was gone.
1999 E430 Sport