Almost sounds like a head gasket, can you smell antifreeze in the exhaust? Does it blow continuous white smoke out of the exhaust? If it does this just when you start it, and then goes away, It could also be antifreeze seeping into a cylinder when it not running. If it were blue smoke, then I would say oil burning. White smoke comes from transmission, power steering leak and anti freeze as well. Check the fluids, that can help you find out what's leaking. If you aren't sure, place card board under your car, under the engine, so you can tell if something is leaking. If it is a leaky head gasket, get it fixed before driving it. You could end up with a cracked head and a blown head gasket. Or worse, cease the motor.