I have an issue like this too. My 2011 e90 has a rattle in what I thought was the steering wheel, but perhaps it is the steering column, when I go over a sharp bump in the road. I removed the airbag and steering wheel in the search for the source, but I couldn't find it. I'm going back in today, and I'm also starting to suspect the steering column lock.
I'm subscribing to this thread and hoping for a fix.