Weird rattling noise in my 2004 Lexus ES330

Hello Everyone-
Looking for some advice regarding my Lexus sedan. It has 88,000 miles and since I bought it used, it has had a little rattling noise that seems like it is coming from the steering column. Originally I thought it might be that the plastic cover on the undercarriage was missing pins, but I had those replaced and still have the rattle. The rattling gets worse the bumpier the road, and there seems to be some shimmy as well…any one have any thoughts on what this could be or how much this is going to cost to repair, or if I should even bother repairing it?
Thanks everyone! Appreciate the help!
Sara