check your sunroof drain, might be plugged with leaves or dirt.
if the track around the sunroof cant drain, the water backs up into the car.
Past: 2001 Orientblue E46 330i
Past: 2004 S60R 6MT
Past: 2007 E90 335i 6MT
Past: 2010 335xi ZMP, BMW Performance Kit, BMW Performance Exhaust
Present: 2013 335i 6MT ZMM/ZDH/ZTP/3AG/494/508