The start-up is not auto-levelling - it's simply to move the motors from one limit of travel to the other. Even halogen cars with the manual thumbwheel do this.
Your headlights will still cycle even if the arm has come off but if the arm is in the wrong position it can cuase the headlamps to aim up or down incorrectly.
Current: 2013 F10 520d M-Sport, Professional Media, Visibility Pack, Reversing Camera, DAB
Previous: 2011 F10 520d M-Sport, 2008 320i M-Sport Coupe, 2002 325i, 2001 318i valvetronic, 1998 318i, 1996 525i, 1990 Porsche 944S2