[jakeru]

Is this a manual transmission? If so, and if only happens on a cold start-up, could be a stiff release bearing that starts working when it gets warmed up. My 2001 boxster base does this, only in very, very cold weather (especially below freezing... haven't gotten there yet this year, but heading toward it) on initial start-up. It should also start working if you apply pressure to it, by simply pressing down a bit on the clutch pedal. Try pressing down a bit on the clutch pedal and see if that makes it stop. If so, most likely is a bad release. If the noise has no relationship to clutch pedal operation (or if you have an automatic boxster!), the problem is something else.