Climate control filter change
Will vary with local conditions. Pull it out, if appears dirty, replace, if clean reinstall.
As Purebred says, a very simple thing you can do yourself. Here is a general overview you may find helpful.
The recommended interval for changing these filters is typically every 15 months or 15K miles, whichever comes first. I recently replaced mine after an interval of about 18 months, and while it had very little visible dust on it, the filter likely contained embedded microscopic grains of pollen, so I just went ahead and replaced it, rather than trying to cheap-out on something that can affect my seasonal allergies.
This is one thing you really need to learn how to do yourself. Dealers want CRAZY money to do it. Just had my car in for a recall, they wanted $70 or so for the cabin air filter replacement! 5 minute job, max, on my car.
Not to mention a huge profit margin on the filter itself.