I am also experiencing this...
AT 2011 335i xdrive
I picked up my car brand new and after 200 kms the spark plugs were done
Car wouldnt start.. Apparently they were soaked in fuel
So they changed all of my plugs but now im getting this stumble around 1500-2000 rpm, the shifts seem jerky and its AT with 4400 kms
But I do drive it pretty soft
What should I do before bringing to dealer
Also how can I figure out which spark plug i should fix if they are all brand new