Sims 3 game shutting off

@loopylottie12  I'm sorry to say it, but your computer isn't nearly powerful enough to run the Pets expansion, at least not with much success.  Pets is the most demanding pack, followed by Seasons, and it's also the most likely to cause crashing and other performance issues on underpowered hardware.  That doesn't mean that this is definitely the cause of your crashes, but it's a strong possibility.  Still, there are other possible causes that should be addressed as well.

I also want to mention that your computer is somewhat low on storage.  It's not an immediate issue, and it shouldn't be contributing to the crashing, but you'll want to watch the free space carefully and clear up another 5 GB or so (for a total of 25 free) if possible.

For Sims 3 itself, please try playing with the EA App in offline mode.  I'm not sure this will help much, but it's an easy to test.

If the game still crashes, please try playing a new save in a clean user folder.  Move the entire Sims 3 folder out of Documents > Electronic Arts and onto your desktop, and when you launch the game, a clean folder will spawn with no content.  Don't add anything to it yet; just start a new save and see how it runs.  You don't need to play that long, or spend much time in CAS: the point is to see whether you get another quick crash.

If the game does crash again, please create yet another clean folder and start another new save, except this time, disable Pets in the launcher.  Please test in Sunset Valley and let me know how this save runs.