sorry I missed that she was a he. If he is neutered I would suggest you take him to the vet as it does sound rather odd behavior especailly out of the blue. There could be that something is not quite right. It is worth a shot. I am not sure what else it could be besides a medical issue. It could be behavioral too. Have you changed anything in the house recently? Have you gotten a new pet, a new baby, spending less time at home, bought new furniture etc. he could be voicing his opinion on the changes if there have been any but the way you discribe it I don't think so. I think a good once over by the vet is in order. better to be safe than sorry.