Cold backed or nasty in the cold?

The person you bought him from told you he was like this and also told you the solution. Just lunge him for a few minutes when it is cold, let him get his bucks out and warm up, then get on and ride as usual. If he's a nice horse and you like him in warm weather, just help him out a little when it's cold and you can continue to enjoy him. And yes, many horses find extra energy when the weather is cooler :)