Could be your battery is low and IBS system is turning stuff
off.(like the stereo)
Battery problems are aggravated by cold.
I would try putting a long slow charge on your battery to
see if it solves some of the problem's before doing anything
else.
Read the first electrical pdf about IBS
electical e90 pdf
http://www.google.com/url?sa=t&rct=j...,d.cGU&cad=rja
http://www.google.com/url?sa=t&rct=j...85464276,d.cGU
http://www.google.com/url?sa=t&rct=j...85464276,d.cGU
Also if I would check your amp to see its not wet.
Amp's going out due to leaks are a common problem in these.
Symtoms are Head Unit appear to function but sound is gone
or Staticy at first before it dies altogether.
Water Drains
https://www.e90post.com/forums/showt...hlight=battery
https://www.e90post.com/forums/showt...hlight=battery
https://www.e90post.com/forums/showthread.php?t=1566005