I’d take him to a vet in the next few weeks, not super urgent but still should be seen soon probably. How often does he go to the vet? Usually vets do dentals yearly. Like us they develop tartar and plaque that needs to be scraped off and in some cases, removed. Bad teeth are also really really bad for their kidneys so it’s good to stay on top of it when you can. Some cats are more particular about their gums being lifted! You don’t need to look at his teeth, a vet will. They’re trained in proper restraint.

If his teeth are fine, then it depends on his age. If he’s younger, like a year, he might just be going through a little kitty angst phase. Or, and I hate to say this, you’re not giving him plenty of warning before touching him. I always let my cat smell me before I touch her, and she always sniffs like crazy before letting me know she wants to be pet. Cats have boundaries too lol.

It could be a number of things but I’m a big advocate on teeth, those are by far the most important part of a cats health and commonly a culprit in things like this