i bought a 528i 2010 3 weeks ago, i noticed the vibration at idle too. no fan noise. took it to bmw yesterday, still under warranty, so they r gonna take a look at it. hopefully they will get it fixed there's also a recall for the 528i 2010 battery rear trunk cable. something like that.

 

decided to come back here to update you guys. so the first time i took my car to the dealer the mechanic said the vibration was normal and i told him it wasnt. they decided to take another look at my car, and after researching a little here i told them it could be the exhaust. they took a look at the exhaust and boooom problem fixed. car doesnt vibrate anymore at idle