Thanks for the info! I think it was a build up, since the days got rapidly warmer (and nights), raised humidity, and him not used to it.
He is doing MUCH better, and even tonight was out grazing with the cows and came up for grain. Only rolled his pasterns a time or two, so I think his brain is reconnecting or the problem is slowly dissipating. Next weekend we have a 2 year old cow due to come into heat, and she is in the same pasture, so I will watch closely to see if he shows interest or tries to breed. That will tell me a lot. He has already settled two cows (prior to his heat incident), so he knew what he was doing before hand.