I have a 2005 325 BMW ci convertible. Sometimes it starts other times nothing.

So does it crank and not fire off, or will it not crank at all when this happens?

Pay attention to when it won't start. Is the engine warm/hot? Is the engine cold? Are the weather conditions wet or damp, like on a rainy day? Intermittent problems are usually electrical. The problem with an intermittent failure is it has to be happening when the shop looks at it. I'd also suggest taking it to a place that specializes in imports. Gas station and chain types of shops are not going to be able to fix it. Neither will your run of the mill independently owned shops, unless they're familiar with imports. Jim