I have one that's been like that for a while, but it doesn't bother me too much. I don't think I'll be upgrading till this one gets worse

This problem is endemic to thin, aluminum and non-stick (amounts to the same thing) pans.

They are heating unevenly in the oven. Because of that, different parts of the pan are expanding at different rates. This leads to a temporary warping, which cures itself when the pan cools.

If it bothers you the only solution is to invest in better grade sheet pans (or, more likely, half-sheets for the home oven). You can get them at restaurant supply places or on line. What you want is either steel or alumisteel as the material, with all steel preferred.

If you're used to non-stick pans, and switch to the steel, better invest in a silicone pad as well, or you'll experience some sticking and/or burning at first.

BTW, if you invest in standard sheet- or half-sheet pans you can also buy parchment paper already cut to fit.

This doesn't work with most housewares type pans because they are not standard sizes as used in the industry. For them you have to buy parchment paper by the role and cut it to fit.

But I Have Become Accustomed To The Popping And Buckling Noises Coming From The Innards Of Me Ole' Oven And Would Think Something Wrong If I Did Not Hear That While Baking Me Cookies!!!

Kind O' Like That Old Car I Used To Have That Made So Many Clinking, Chugging, And Churning Noises Forever, As Soon As I Changed The Oil And Did A Fine Tune On It Wouldn't Ya' Know Tha Darn Thing Back-fired Once And Gave Up The Ghost!

There's An Old Proverb; If It Aint Broke Don't Fix It, And It Aint Broke Cupcakecook!

Invest in good pans - you wont' be sorry! Ditto with cooking pans. Ditch the aluminum pans - not good for you anyway. Even if you have to buy them one at a time - it's well worth it.