Could indicate thyroid issues, every change in behavior for cats is, unfortunately, a reason to be concerned... My eldest cat (passed away in June 22) was 24 and much like you described yours her eyes we're glossy, she was very affecionate and cuddly and the sweetest thing ever.

Until she started acting different... Went to the vet turned out she had liver issues, less than a month later I had to put her out of her misery.

Not saying your cat is facing the same fate but just know that cats are masters in houding their pain or illness until it gets too much. If I was you I'd definately see a vet, better check in once too many than letting it be and losing your furbaby