I've had the same problem since I got my X, with exact same symptoms. I have a recently replaced battery and alternator, and was showing no other electrical related problems. I never found any threads on here with info, so I researched all over the place and finally found the following SIB on an E38 board, but it also applies to the early X5 4.4i.

Since reading the SIB below, I don't worry about it as it seems to just be a DME error and not something mechancal (such as the ignition switch).

You can likely have the dealer reprogram/update the DME if you prefer, but I just live with it as it happens occasionally and hasn't caused any problems.


"Service Information B12 20 06

SUBJECT
Intermittent "No-Crank, No-Start" Condition


MODEL
E38 740i, 740iL with M62TU up to 04/04

E53 X5 4.4, E39 540i with M62TU up to 09/03


SITUATION
Customer may complain of an intermittent "no-crank, no-start" condition. When starting vehicle, only a "clunk" noise can be heard from the starter. Vehicle starts on a second attempt. No faults are stored in DME/EWS control modules.

CAUSE
DME error."

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Now:
E53 4.4i Sport
E39 /// M5
back then:
E36
E30 (x2)
E21