It is hard to tell you why TurboTax is asking you to fill out form 8959 without knowing the details of your return.
You can read the IRS instructions for the form here: Instructions for Form 8959 (2023) | Internal Revenue Service (irs.gov) and look at the "Who Must File" section to see if any of those conditions apply to you. Typically, this form is used to calculate additional Medicare tax you must pay because not enough was withheld by your employer or you had self employment income and not enough Medicare tax was paid by you (or your spouse). You also need to file this form if too much tax is withheld. If you report more than $200,000 of Medicare wages and tips on any single W2 (box 5), you may have to file form 8959. If you make more than $250,000 (married filing jointly, other situations have other limits) then you might have to pay additional Medicare tax and that means you have to file form 8959. If you report more than $160,200 on a single W2 and your or your spouse are reporting a second W2, it is possible that too much Medicare tax was withheld and you need to file form 8959 to get the balance refunded. If you don't think any of these conditions apply to you, recheck all of the numbers you entered from your W2's and anything you have reported regarding self-employment income (Schedules E and SE, if anything) -- something in there is triggering TurboTax to want to file form 8595.
