I use an 8GB flash drive plugged into the USB port, and I have my artists and albums grouped by folders. I am able to shuffle the songs by choosing Songs, then tapping the iDrive controller and choose Random. See if this works for you.
F85 X5 M on order
| 2008 E92 M3 Coupe 6MT
| 2009 E70 X5 xDrive 48i M Sport
| 1967 Corvette Coupe
2001 E46 M3 - Sold | 1997 E36 M3 - Sold | BMW CCA member