steering wheel clicks/rattleswhile steering & over bumps

The rattling of the steering wheel is annoying as well as, going over bumps. Other people hear this & I am embarrassed. My mechanic isn't sure what's wrong so I know I need to go to dealership. Worried it will cost me a lot to fix but I am concerned about driving it much longer w/o getting it fixed. Just wanted to see if others had the same problem.