White smoke might be an indication of blown/damaged Head Gasket leading to the burning of coolant inside combustion chamber. I owned 2006 model. Car had the same problem as yours plus it used to randomly heat up. It's head gasket was damaged. I got head gasket replaced and it's head repaired. Sadly enough, I had to replace head gasket 3 times; 2 times from Lahore and 1 time from Karachi but problem still persisted. Head gasket kept blowing up. I still don't know why. Stopping car while driving, might be a setting problem of fuel injectors which a good mechanic can fix.
You need to find a good mechanic for that if it's really the head gasket issue. If smoke color is blue+gray then that's the indication of worn off Rings/Pistons making the engine oil leak into combustion chamber. That means you'll have to have them replaced.
Did you notice that when you are accelerating, car seems ok but sometimes just when you remove your foot from accelerator (for braking or slowing down), engine is turned off? If that's so, it's setting/timing problem which a good mechanic can fix.
P.S: I am not an expert. Above was my experience which I shared with you. Some other expert from the forum may give you the proper advice. For that, also mention how much kilometers car has covered as per ODO and which model (year) is your VXR.