First start takes ages!

[insertnamehere]

Just done a search but got about 4,500 "answers" so,

The first start of the day in my 318i is pretty appalling, it takes at least 2 or 3 tries of about 20seconds to fire up. Once it's done it's first start it's fine, even if you switch it straight off before it's warmed up it will start first turn after about 1.5/2 seconds.

While this doesn't worry me too much I'd like to get it sorted as cranking for that long can't do the starter much good & will also end up "cycling" the battery & no doubt leave me stranded when I least need it!

Any ideas? I'm thinking maybe an air leak allowing the fuel filter to empty back to the tank or something like?