Already had that on my E90: radio logic 7, cluster and flashers were not working. The car was running great. Checked all the fuses and everything was normal. Next morning, all was normal... Never knew the reason and never did it again the next 2,5 years. All I know: there's a recall for bad battery connexion.
Also, it's an optic fiber between your radio and amp, maybe it's broken.
Recall 61 80 13RC
SUMMARY:
BMW is recalling certain model year 2008-2012 1-Series coupes and convertibles manufactured December 2007 through July 2011; and 2007-2011 3-Series coupes and convertibles manufactured March 2007 through July 2011; 2007-2011 3-Series sedans manufactured March 2007 through October 2011; 2007-2011 3-Series sports wagons manufactured March 2007 through June 2011; and 2009-2011 Z4 vehicles manufactured March 2009 through June 2011.
The connector for the positive battery cable connector and the corresponding terminal on the fuse box may degrade over time. Over time, the high current flow and heat from electrical resistance may lead to a breakage of the connection, and a loss of electrical power to the vehicle.
CONSEQUENCE:
If there is a loss of electrical power to the vehicle, the vehicle may unexpectedly stall, increasing the risk of a crash.
REMEDY:
BMW will notify owners, and dealers will replace the positive battery cable connector and secure it with an improved method, free of charge.