Cat chews on air?

[ScottishNewbie]

I rescued two kittens from Blue Cross last year when they were 9 weeks old.
One of the boys (Wolfie) has had this odd habit from the moment we got him.

He will turn his head slightly and chew up and down for about 30 seconds and then stop. He likes to rest his face against corners of things, he also seeks out my fingers to do it against, but he will also do it while sat upright with nothing near him.

It's a proper chew up and down, not a suckling if that makes sense.

I have taken him to the vet about this and she did a thorough mouth check and watched a video I took of it and basically shrugged and said it was most likely a behavioural thing.
But it still worries me as I would hate for him to be in pain....but if not a dental or mouth issue, and the vet is stumped, then it's probably benign?
Does anyone have any ideas?

Change of diet had had no impact whatsoever. (Wet and dry mix, now solely on wet).
Also not environmental as have moved house.
He shows no signs of stress or anxiety. Very relaxed, eats and sleeps well.

Could he have a bit of cat hair in his mouth? My cat is long haired and does a similar chewing thing when she gets a bit of her fluff in her mouth.

@autumnapplepicking I did think that at first, but he's done it daily for over a year now...it is possible though!

My cat does the same! Looks like he's chewing Tobacco in a western

@Holly05235892 oooh, yes! Thank you for your reply!
Do you have any ideas as to why he does it?

Mine loves gnawing wall corners. She does the western tobacco chewing thing too but I think it’s her fur. But yeah nibbling and chewing wall corners that’s odd and she does it all the time.

@ScottishNewbie Honestly we've just decided it's a habit. Like yours, hes done it for years so hes not in any pain or irritated or anything. It's just part of his funny personality!

Okay, I'm feeling better! Thanks guys!
It seems my little oddball isn't alone