blue smoke on cold start up

Hardened valve guide seals are the logical suspect if the smoking stops very quickly. Oil runs down the valve stems into the combustion chambers when you stop the engine. That can be aggravated by excessive gas in the oil from a previous running problem. That will clear up once all the gas has vaporized and been drawn out.

Your engine really isn't old enough or has enough miles for this to occur yet but that is the only thing that will cause smoke only at start-up.