Hello everyone, I have a 99 Nissan altima that has smoke coming out from under the hood. After letting the car sit overnight I tried starting it up again and it starts up just fine but there seems to be smoke coming out from the alternator. The smoke seems to be white and it took about 10 min before I started seeing smoke. Do you think it is the alternator? I checked the belts and they seem fine. I also just had a new radiator put in about 2 weeks ago so that seems fine as well.

White smoke is usually from coolant. Check for a warped head and blown head gasket. Don't drive the car, if this is the situation--it's easy to damage the valves.

Is there a way check for this without taking everything out?

Look for an antifreeze leak around the head. Antifreeze also has a very characteristic odor. Also, you can remove all of the spark plugs and check the compression of each cylinder. Write the results down on a piece of paper and compare pressures. Much can be gleened from the results.

So I took the car to the mechanic and they weren't able to find anything. They said to keep driving it and if it kept happening to bring it back. I've gone to these guys for years and they never steered me wrong.
So I did, next day, whole car shuts off, no power or anything. It ended up being the alternator that was smoking as I, and a friend, had originally suspected. So my mechanic replaced it cheap, and now it's back to business as usual.

Thanks all for your advice anyway.