It could be kitty dementia. I know that as my RB Storm aged, he would also start crying for no reason at all. At first I thought that he was in pain but he just seemed to be very confused or lost. I would talk to him and this seemed to help to calm him down. It's so hard to watch our animals age. Hopefully whatever is causing these things with Oatmeal isn't anything too serious. Maybe you should bring him to the vet for a senior check up just to on the safe side.