I have an outside kitten named Rascal. He is 5-1/2 months old. He was neutered a week and half ago. He's been out with the other cats. They have access to a garage which is heated to about 50-55 degrees. We live in Wisconsin and it has been cold but not bitter cold yet.For several days now he has not been acting like himself. He's been sitting under the outside dryer vent when it's running. Otherwise he's been just laying in the garage. He is able to get up on a box so he is not on the cold concrete floor. He will curl up with 2 other kittens his age. He doesn't seem to be eating as much. I let him in the house yesterday and he just laid around. Had no interest in food. I even put out some salmon wet food that I had and he refused it. He would shiver every so often. I did put him back out last nite and today I let him in again. He seemed to have more energy and I gave him some of the wet food which he ate with gusto. He then went and laid on the floor register when the heat came on. While sitting there he just shivered. He wouldn't purr yesterday but today he has been purring all the time. I got out my heating pad and right now he is up on the couch on the heating pad set on low. He did shiver when I first put him on it but not anymore. He's sleeping right now and seems quite content. Should I be concerned about his shivering? He just got up. Got off the couch by himself but is quite wobbly on the side that he was laying on. As he walks around it seems to get better. I'm thinking of leaving him in the house tonite. I do have another cat in the house but she seems afraid of Rascal and runs away from him so I don't think there will be any issues there.