Cat wheezing when I pick him up

[Chainedtomato]

7 year old male cat, as far as I can tell he is fit as a fiddle. He is slim, goes out all the time, eats, jumps, plays etc.

However recently in the past few months he is making a distinct wheezing sound when I pick him up. I pick him up the same as I always have. Had lots of cats over the years and pick them up with care but never come across this before.

Any ideas what it could be and if it’s worth a trip to the vet?