@LoraLovesTheSims First of all, you won't lose your owned content (the base game and packs) if you uninstall and reinstall. Your Origin game library owns these, not your computer, and you have the right to install the game as many times as you want, on as many systems as you want. Your saves and other user content are in Documents\Electronic Arts\The Sims 4, and you can make a copy of that folder to preserve it before uninstalling. (The folder isn't supposed to get deleted, but there's still a chance, so better to have a backup.)
Having said that, you don't necessarily need to uninstall and reinstall. Please let me know what you see when you press Play. Please also run a dxdiag and attach it to a post.
https://help.ea.com/en/help/pc/how-to-gather-dxdiag-information/
And let me know what antivirus you run.