Game constantly shutting down

Without CC and Mods, the options are pretty limited on what is causing this and how to fix it. 

1st. Backup your Saves and Tray. 
Then. Do a Game Repair. 
If the Game Repair doesn't work, you can try a Soft Uninstall. 
(To Do This: Remove your User Settings Configuration, Saves, Tray, and Screenshots (if important) from TS4 folder. Then delete the entire folder. (Make sure the location is: Documents/ElectronicArts/TheSims4 <---  Start your game as usual from the EA App, it will reinstall, but take less time VS a complete uninstall. 

If a Soft Uninstall doesn't work, the only other option is to completely uninstall and reinstall. 
Don't worry, you shouldn't lose your playtime hours, but make sure you create a backup of your Saves, Tray, Screenshots, and User Settings Configuration because YOU WILL LOSE THOSE if you don't. 

If that doesn't work, report it as a Bug over in the Bug Forums.