mine turns off now and then. aswell sometimes i go to change playlist or artist and it says please wait while library is updated blah blah blah or something,
As an earlier post said and this is vital:
START THE ENGINE WITH IT NOT CONNECTED. PLUG IT IN AFTER START-UP AND ENJOY YOUR JOURNEY.
Mine works absolutely perfectly. The trouble is that if you stop for a moment and turn the engine off (e.g. when I fill up / close the garage door etc) and then back on, it's easy to forget
You've just got to make it a habit - turn the key, unplug the USB.....