Inconsistent front end vibration
2003 325Xi, manual trans. 80000 miles. Sometimes I get a substantial vibration in the front (feel it through steering wheel). Not speed dependent. Not transmission gear dependent. Still there when driveshaft is "unloaded" (coasting in neutral). When vibration occurs, can come to a full stop, and its usually not there when getting back up to speed. Then after a few miles it sometimes reoccurs. Sometimes not. No vibration when braking. CV joints (they seem good - only a tiny bit of play)?? Wheel hub bearing (that wouldn't be inconsistent)?? Other ideas please??