Your cat is suddenly vomiting mucus that looks like snot, which could mean he has some medical problem. Here are some possible reasons for this: 1. Indigestion: If your cat eats inappropriate food, or consumes too much food, it may cause indigestion, which can lead to vomiting. 2. Feline distemper virus infection: This is a serious infectious disease that may cause vomiting and other symptoms in cats.

3. Parasitic infection: If your cat is not dewormed regularly, it may be infected with parasites , which may also cause vomiting.

4. Hairball syndrome: Cats may swallow too much hair when grooming themselves, forming hairballs, which may cause the cat to vomit.