Your cat may be reacting to a scent that you brushed against while you were out and about. You may get this scent in a spot you frequented on those days; unfortunately, you may be totally unaware of the scent yourself. Also, your cat may be bored and is looking for something to do. Since cats are natural hunters, he is hunting you. For this, I would try playing with him a lot more. Give him his own furniture and a place to climb with a view outside to occupy him. If your cat is not fixed, I would get that done as soon as possible to reduce his hormones from causing him to act irrationally. If none of these things help, I would ask my vet about a possible chemical in-balance that causes the attacks.