Driving along other day and i hear a sound almost like a high pitched shrieking. I thought it was the radio, but after turning that off I realized it was coming from passenger front wheel area. I lowered passenger window and it was quite distinct. I pulled into a lot to check it, looked in the well, tire, etc.....sawnothing.Restarted, took off, and sound disappeared ( drove 20 miles home). Yesterday, heard a similar sound, but quite reduced and only for a few seconds, and it ended when I braked. Drove another 5 miles or so and sound did not re-occur. I have a 2007 ML 320cdi with about 9500 miles. It was just in this week for an oil change. I'd go back to dealer, but dealer is an hour away andI'm supposed to leave for vacation tommorrow.Anyone have any thoughts on this?