How come sometimes one hand is warm, and the other is really cold?

I'm having that a lot, and there is no breeze to my other hand.

Probably circulation. When you remain in one position for extended periods of time you can get differences in circulation. See if exercising changes it.

Well this is the only thing I can say I get that too but don't why .. I have Arthritis but doesn't mean you have it too but it could be something else. I guess..

Circulation is always the first thing to look for in cold hands; like Rob said try googling hand circulation excersises and if those don't work see a doctor.