435i Rough cold start idle

[spindizzy]

My 2015 435i M Sport auto has started to randomly exhibit a cold start idle problem that make it ALMOST stall after a cold start. Transmission not engaged at any point. It starts fine, goes to 1200 rpm then the revs drop slowly to 1000 then suddenly to about 500 rpm whereupon it splutters then goes back to 1200 then steadies to a perfect idle. Seems unrelated to outside temperature and I regularly use the same fuel station (VPower) but there seems to be no correlation between fill-ups and whether the problem happens. Trawling the net and forums has not yielded a definitive answer, just possible causes. Quite a few people with the N55 engine seem to have had similar issues.
Its done 60k miles (all me) and has had new plugs and a recent oil change. It has had the problem both before and after the plug change. It went away for weeks at one point but has now resurfaced.
Anyone out there had the problem and had it fixed?

[Allanv]

Not the same car but my 330i N53 stated having the cold start idle issue and it turned out to be a couple of injectors.

But could easy be coil packs, I would get the codes read to see what is stored about the idle.

[spindizzy]

Update on this issue having had the car in for its end of warranty check, MOT etc. The engine falter had become more frequent and I provided full details to the dealer (who supplied the car new originally). They said they had discussed it with BMW who surprise, surprise said it was "a normal part of the cold start cycle" and won't do anything to fix it. It may be normal because their engine design is such that they develop faults after 55k miles (which is when it started happening). Whilst the issue is not hugely significant at the moment, I find the suggestion that an intermittent fault is "normal" and therefore not worthy of fixing to be preposterous.