My 2 and a half year old cat sometimes sleeps so soundly that I think he is dead. He is cold and limp and I panic at first, but then he comes around. He is very strong and healthy, and very trusting and laid back, but he's literally "out cold". Of course, the vet said to bring him in for a bunch of tests, but she also said she'd never heard of this before except in older, and maybe sick, cats. Has anyone else experienced this and should I be concerned that he has a health problem?