It is normal to get a little smoke(from condensation buildup in the exhaust) but not a lot every time you start it out of the exhaust, but what do you mean smoke from behind the engine? If it is coming out of the engine compartment the answer is no.(If you do it could be as simple as an oil leak) What color is the smoke? How long does it last? Does your coolant and oil look normal and are they at the proper levels?