Chemistry, attraction, and all other things frustrating & desirable

Someone sat next to me the other day, and the half of my body next to him went numb. Well, not numb, but paralytic. I wanted him to talk to me, show me attention, and he did. I wanted him to sit next to me and, even though it was surprising, to put his thigh so incredibly close to mine. So why did I freeze up? How can I not do that again? Will there be another opportunity in which to do things differently? How can I talk to him about this, and should I? Am I making a big deal of nothing?