Unusual white smoke and another unusual thing

All days their comes a little black smoke out of the exhaust when we start it up but today for a while when driving their was a big white smoke screen when driving and I also noticed that sometimes when we were driving on the highway it felt like the car was shaking. Ait is almost unoticible. I think it is the engine cutting oit just for a splut second a few times but I do not know. When the cars "hkakes" its only for a very short while. Do you knoe the cause of the problem and hoe can I fix it