I have the same problem, got comfort seats drives me mad. I've just had the front passenger headrest relaced as it vibrated, especially when the cars cold, seems to have sorted that vibration, however theres another coming from under the seat. If you look under the back of the seat theres a grey cable that runs down the back of the seat and under to a blue connector, thought I had cracked it by moving this away from the metal frame it was touching slightly but its back again !! Anyone who has any ideas what this could be would be appreciated.