Q. What could be causing my 20 year old cat to all of a sudden be scared of me? He is eating/drinking great, he seems to see and hear fine.
A. It maybe that something has spooked him and if you were in the vicinity he may have associated it with you, ie a loud noise. Sometimes they can act differently if something has changed in the environment such as a new member of the family, New furniture, even change in washing detergent. It could also be a neurological problem especially considering his age. I would recommend having him checked by your vet to rule out any medical cause.