2001 Chevrolet Impala What could it be.

Recently my car has been smoking. A white smoke comes from underneath the hood about 15 minutes after being crunk. Its not overheating though. There is also a burning smell and an unknown smell coming through the vents. I lifted the hood and smoke was coming off the engine. Any idea what this could be? Also every few weeks I have to put coolant or water in my car because it starts to over heat. I don't have a problem with it overheating afterwards but why must I repeat this so often? Then recent I started to hear a sound when I crank my car as if my belt is squeaking. You would think its the belt but its something about while im cranking it, that sound seems as if its apart of the crank system. It doesnt do it everything I crank my car. Most of the time I just turn off the car and re crank and its fine. Any ideas on this?