[Mrmerlin]

this is a normal condition .
The exhaust system has not reached operating temperature though the cats are getting hot as this heated air cools the water vapor in the exhaust condenses and forms the smoke that you see, once the pipes heat up enough then the air is too hot condense to the vapor point, this then will cause the smoking to stop.
In very cold conditions an exhaust may smoke all of the time as the air is cold enough the cool the hot air to the vapor point quickly before it has a chance to disperse