what's wrong with my car and how do I fix it?

well the smoking is probably the oil burning off the engine. as far as the jerking and cutting off, how well do you keep the car maintained?

The smoking is related to the oil leaks - most likely oil is dripping on the exhaust manifold. The "trying to cut off" sounds like an air intake problem. Clean the air filter, MAF sensor (if it has one, use MAF cleaner), EGR or PVC valves, replace the IAC (idle air control valve), clean the throttle body (they make sprays just for that). Google Youtube videos for how to clean/replace these parts. This is just a simplified response to your question, you might have more serious issues going on.