I have exactly the same noise from mine on start up, a few loudish knocks and only lasts about a second.

Will be interested to hear further replies.

__________________
2009 E70 X5 35d M-Sport
Black Sapphire / Tan Leather - LCI Tail Lights

Sold - E53 X5 3.0d Sport
Black Sapphire / Black Leather - OEM 214 type alloys - Wheel Arch Extension Kit - Depo A/E Headlights - 55w HID's - LED Tails - M3 S/Wheel - Black Kidneys - LED Int Lights.

Sold - E53 X5 4.4i Sport