1524415 Did you add any content to the game: mods, custom content, downloads from the Store or Exchange? If so, please remove or rename the Sims 3 folder in Documents > Electronic Arts and try again.
If this doesn't help, or you didn't add any content, does this happen when the Sims 3 launcher opens or when you press the Play button? Do you use a third-party antivirus or some kind of cleaner app?
Please also list the full specs of your Mac: everything under About This Mac including the operating system and except for the serial number. And list the free and total storage as well.