Okay guys, I just purchased a used 2004 100 series a week ago. Yesterday, while driving, I heard a vibrating noise (cell phone vibrating-type sound) randomly. I heard it maybe 6-7 times during a 45 minute drive. Has anyone else heard this. It wasn't a cell phone...that was the first thing I checked. Wife thinks it could be the air conditioner....what do ya'll think? Thanks.