Heavy breathing in 1.5yo male cat

Video - https://streamable.com/3kpygw

Hi everyone!

I noticed the past couple weeks that my cat has been breathing heavy during his rest/sleep (shown in video above). Is this pattern something to be concerned about?

His lungs sound clear after listening through a stethoscope. Not sure if this is relevant but he did have a endoscopy last month for swallowing a bunch of cotton balls.

Thanks in advance!