1999 Deville smoking

First time I have seen it smoke was today. I started it and everything
seemed fine. Left the driveway and started down the street.  Saw my
son driving up so I stopped and put it in park. Shortly thereafter it
started billowing white smoke from the exhaust.  I put it in drive and
started moving and the smoke stopped within 25 feet. No more smoke
during the trip while moving or stopped.  

I checked the oil to see how it looked.  It looked like oil with no
water or coolant.  Not sure what else to do.

I am planning to take it to the dealer to have it checked and I would
like some advice on questions to ask or tests to have done or any
other helpful advice you may have.

Thank you 

Smokey