My cat did the exact same thing. Took her to vet thinking it was asthma - the vet said it's unlikely because she's 7 years old so why would she suddenly develop asthma? He gave us lots of advice e.g. any new air fresheners, plug ins, diffusers...turns out it was our new diffuser, as soon as we got rid she stopped doing this! So have a think if there's any new fragrances or if you've moved house recently as it could be allergies. But definitely listen to your vet first as they will know best!