Engine noise '06 Boxster S

[Biang]

Has anyone ever had this problem?

Background Info: I have a 2006 Boxster S with 13K miles. Never driven in the winter. Oil changed every time it went into storage in October.

Problem: Once or twice a summer, I get a noise when I start the car in the morning (not driven since the evening before). (Never happened when the engine was warm) The engine starts up and there is a noise coming from the engine that sounds like a chain rattling. It lasts less than a second. The engine runs fine and there is no smoke coming from the exhaust. It almost sounds like the timing chain is loose (that is, if Porsche uses a metal timing chain). When the car gets out of storage in late March I will take it in for its 4 year service and get Porsche's opinion but I am worried it might be serious.

Any help?

Randy