@MaryFarris14 It's possible that the problem here is too many performance career limos spawning in the background, which is a problem in Starlight Shores. It could also be something else of course. At any rate, please add NRaas ErrorTrap, Overwatch, MasterController, Register, and Traffic, all linked here:
https://answers.ea.com/t5/Technical-Issues-PC/Sims-3-Common-Game-Fixing-Mods-Hero-Approved/m-p/9838855#M244208
That post also has a link to instructions for installing mods in case you need them. MasterController doesn't do anything unless you use it to issue a command; the others do their cleanup in the background, without the need for user input. Traffic is the one that would prevent the excess limos from spawning, with Overwatch cleaning up those that already exist. ET and OW do more general cleanup as well, so they're great to have for the overall health of your save.
Load your save, and let it run for a few sim-minutes, until the mod-related notifications in the upper-right corner of the screen have cycled through and stopped appearing. Use "save as" to rename the save, so the original remains intact as a backup. Quit the game, restart your computer, reload the save, and see how it runs.
If you still notice any problems, click on City Hall and select NRaas > MasterController > Town > Reset Everything. This can take a couple minutes to run, depending on the complexity of the save and the speed of your computer. When it's done, let the game run for a few more sim-minutes, then "save as" and quit and reload again.