BMW Repair: 328xi 2007 little motor sound on closing door, 2007 bmw 328, 325is

Question
I buy a 2007 bmw 328 xi 4 doors and somethime there is a
sound of a little électric motor sound just after closing
a door like when i close the trunk... The dealer don't know
what it can be... I imagine it is to look whit a bar the door but it is not each time...

Answer
I am thinking that the windows must open slightly when the door is closed to prevent other issues happening as the vehicle has a tight seal inside.When you open the door do the door windows come down slightly?if so that maybe what you are hearing.I have a 325is here and the window does come down slightly then roll back up when the door closes.