Buzz when opening door

[britboy_atl]

Hi everyone. My 2005 Cooper S (completely std) has developed a strange buzzing sound. It occurs when I first unlock and open the door and I can hear it coming from the central dash area. It only lasts a few seconds and then fades away.

This happens without the engine on or the key in the ignition. It sounds like an electrical noise... almost like a lighting dimmer or some sort. Since it hasn't always done this, I assume this isn't by design. Does anyone have any suggestions on what it may be or a fix?

Thanks!