2000 Chevy S-10

Recently my car has been hard to start but only when its just after it has been running. So when the engine is still hot. Sometimes it just doesnt try to start at all and sometimes the whole car will shake in an attempt to start. If it does start after that, it idles extremely low as if its going to stall out. And sometimes it spits out a little, very thin cloud of white smoke. It has also done it at times when I just stopped and I see it go by. Is this a serious problem? And what is causing it?
i just replaced my alternator and got a new oil and fuel filter. I changed my oil and coolant and there was a little leak on the piece that connects to the carburator( im not sure what that piece is but I know air goes through it) that I temporarily plugged up.
i have a book for my car and it doesnt say anything about this really. So I need help.