Vet said nothing is wrong with him

My friend's cat has these episodes and the vet was not helpful. Just said "thats weird" in response to the symptoms. Was wondering if anybody had any advice. "We ran a full panel blood test and everything came back normal. It doesn’t happen all the time but when it does it’s usually at night and he acts fine the next day. But like he won’t eat during his episodes and he’s very food motivated usually. He won’t drink either. Very lethargic and just lays there and breathes kinda fast until his episode ends. And obviously the drooling. And he doesn’t have the steadiest gait (but that’s all the time, not just during an episode) they ruled out anything ear related like vestibular stuff. He tested negative for the FIV/FLEV stuff. And has had his rabies vax and is neutered. He’s around 8 months old and he’s been doing this since he was like 3 months old when we got him"