cat’s breathing is odd, what could it be?

my cat is around 6 months old, i found him when he was 2 months old (around july) at my work. it was a fruit plant, found him underneath machinery with a bloody nose and so many fleas, his breathing also seemed a bit congested but after a few weeks it went away (along with the fleas) and i never heard it again. i took him to get a checkup and neuter in september and his vet said everything was good and the kitty was healthy. fast forward to november, he’s starting have this strange breathing pattern and i have no idea what’s going on, i need his booster but got his other vaccines. he’s usually begging for food and today i noticed he would meow for the food but when i gave it to him he would sniff it and leave. i noticed that he won’t eat it if his breathing it like the video above but if his breathing is normal he’ll eat, he’s usually always begging for food and playful, but today it’s like a flip switched. i’m currently scheduling an appointment for my kitty but if anyone has any insight or ideas of what it could be it would mean a lot. thank you! hoping my kitty is going to be okay.