I have a rescue mom and 3 kittens. One of the kittens was born with back legs deformed. Twice now I have picked the kitten up to cuddle, it rolls on his back, belly up as I rub him. All of a sudden he starts to go limp like he is dead. His inner side kids close in. I put him up right and his head just dropped over like he died. This is freaking me out! I start rubbing him and talking to him to wake him up. With in seconds he comes back. What could possibly be happening? Do I need to take him to the vet?