Rough Idle at startup...sometimes

[lucardo]

Hello! Bought a second hand 2010 X5 30d with 120K kms, car runs great and very happy with it, love it actually.

Most mornings I get a rough idle when starting the car. The car starts, revs up to 1K, after a couple of seconds the revs lower and the roughness starts, goes on for about 10 secs and then the car runs fine. No lack of power, no smoke, no smell, no engine light no error codes. Never does it when warm or after sitting for a couple of hours, only when starting completely cold. Sleeps in garaje so low temperature is not an issue.

Took it to an indy and found a fault on glowplug 5, changed all plugs but still getting the rough idle. Doesnt happen every morning. ´The car isthere right now and (of course) he cant replicate the problem...

Any idea what it could be?