I think that we have seen this questions asked a few times already within the past few weeks. I think you might be having power issues due to a weak battery. I think from a 04 to a 06 model, depending on driving pattern, it's about time for the battery to be weakening, so might be time for replacement.

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2008 650 Convertible- 6 Speed manual- Sport package- HUD- Lane Departure- Comfort Access- Merino Leather- HD Radio- SAT