Does it happen only when you unlock the car and are you inside the X5 and is your door open or closed when you hear it? I get a clicking noise towards the rear wheels, so I assume it's the air suspension activating and the springs expanding. I hear it more on cold days, but I'm not sure if that's normal. I ask if your door is open when you hear it because it's possible that it seems like it's coming from the dash because the sound is reflecting off your windshield.

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