your alternator is on its way out. x-mas tree effects will occur again when the alternator death leads to killed battery. have them replaced now or you will get strainded later. i had this issue 2 weeks before the battery went out then alternator went dead causing the engine to use the battery to power up the car and eletronics, then the battery and the alternator died at once when my wife was driving it on highway. scary stuff. everything shuts off no lights, nothing. she was able to pull over the shoulder and get it towed.

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2002 X5 3.0 Siena Red
Premium, Cold Weather, Rear Climate Packages, 19" Wheels
Aluminum Running Boards, Clear Tail Lights, Clear Side Markers
Titanium Kidney Grills, Titanium Trunk Lid, Xenon Headlights
4.6is X5 exhausts, 35% Tint, Aluminum Pedals
2005 530I Mystic Blue
Premium Package, Sport Package, Xenon Headlights
18" Sport Wheels, 35% Tint all around
Mods to come: M-Tech Front Bumper, M5 Side Skirts, M5 Rear Bumper
Quad Exhausts, Style 172 19" Wheels