Probably the seals around the doors/windows, they will squeak if you put most any dressing on them. Wipe down with a 3:1 mix water and IPA to remove the dressing, then wipe again with water only. If you dress them use Gummi Pflege or SwissVax Seal feed. The Gummi is way cheaper. Or do not dress them at all.
08 E90 335i Monaco Blue Gray Dakota ZPP ZSP Heated Seats CA Step w/Paddles iPod