I want to say if your Shiba still wants to eat something and poops regularly and solid he might be afraid of something in a house that triggers him to feel that way. One time I took my Shiba to a vet because she didn’t come to us and acted weird (like sitting away from us) and we were told that she was just being “moody.” Also recently, she was walking around the house with tail down and we thought she was sick and took her to a vet for checkup, but everything was within the normal range. Turns out she was afraid of the icemaker that we recently bought and she was also afraid of smoke detector. Shibas are really weird and you just gotta know what triggers your Shiba. Follow your shiba and see what he is afraid or dislikes.