A stale smell that improves briefly after startup can mean dust on components or a dirty filter

https://localcoolinghelp727.zenbloomer.com/posts/what-homeowners-in-florida-should-do-when-the-ac-breaks-down-in-the-heat

A stale smell that improves briefly after startup can mean dust on components or a dirty filter. Replace the filter and have the system cleaned if odors keep returning.