Marc, it sounds like the intermediate levers problem. All 2004-06 engines (N62) use this system to control the throttle. Sometimes they wear and do the problem you have. Fixing it is a bit expensive. Most people experiencing this problem just turn the engine off and restart it like you do.

This is a known problem and there are many threads on this subject on this forum. Here is one example:
http://www.xoutpost.com/bmw-sav-foru...-need-fix.html

BTW, I see you are from Montréal, are you a member of the BMW club?

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