I drive a 2002 P5 with about 35,000 miles on it that has a manual transmission and everything is still stock on it (living 2 miles from work is pretty sweet). Recently, my car started vibrating when I'm driving it at random times. It started out being not that often, and in the last week has progressed to more often. But there is still sometimes it doesn't do it. It doesn't vibrate when it's idling, the idle is still smooth. But when I'm driving there is a noticeable vibration. It could happen as soon as I take it out of park, or it could happen when I downshift or upshift. Any ideas what the problem could be and how much it would cost to fix it? Thanks.