The vehicles come prewired for a lot of options. Could be a connector for something not on your vehicle.
Get the wire colors and check the TIS online.

https://www.newtis.info/tisv2/a/en/e53-x5-3.0i-sav/

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Sent via Telegraph Wires using my Morse Key.
2021 X5 xDrive40i
2015 X5 xDrive35i MSport
(Traded) 2013 X5 xDrive35i