2001 Toyota Avalon oily smoke

I just bought a 2001 Avalon that has only 67,000 miles and runs great (clear CarFax). When I started it this morning, it initially emitted a lot of oily smoke, the kind made by cars whose engines burn oil badly. As the car warmed up, the smoke dissipated, and it spewed no smoke while I drove it to work. It did the same thing on the sales lot, but the car had been sitting idle for about a week and the oil had just been changed. (As I do in all of my cars, I have planned to switch over to synthetic oil.) Should I have any real concerns? Should the oil change help? If it perhaps had synthetic oil before the dealer changed the oil, might that be the problem?