I have had my '99 Boxster for a few months. Pristine condition. Low miles. But twice now, after not having driven it for a few days, I start it and a puff of white smoke blasts out of the exhaust.
Stevenson927, common to boxster especially you the car was seated for few days. If just a quick white smoke from cold start and it goes away just before you drive it, nothing to worry. But if the white smoke stays for awhile or while driving it, first thing to replace is the AOS (Air Oil Separator) and maybe check engine will trigger also.
Not really hard to replace if you have a little knowledge with DIY cost only less than $140 for the AOS part.
This would also happen if I parked my boxster on a steep angle downhill... oil must accumulate just right to puff. AOS is worth looking at/ installing a new one. About 2 hours of time and a 35$ part was what it took me on my first go around.
Make sure your oil isn't over full. I had an issue when the oil bars on the dash were completely full I let out a filter full and put the filter back brought it down one bar and it was great. My understanding is that it's a flat 6 engine so if the oil is slightly high it will sit higher than the ring and seep through as it sits.