The battery light on my bmw 323 ci keeps flashing every now and then, it always happens when i turn the car on and keeps flashing for about 10-15 minutes and then just switches off again. Sometimes it'll start flashing whilst i'm driving. I haven't got a clue what could be causing it, so any help would be appreciated!!!!!

Your "battery" light doesn't really warn you about low battery, but whether your battery is receiving charge from your alternator.

If it comes on, that means your alternator (or charging circuit) is dying.

A cheap (free) way to check this is to go to any Autozone... they have a push-cart with an alternator tester. They can check if your alternator is working properly with your car in their parking lot.