Random Game Crashes?

First, keep an eye on RAM use while you play. You can have the Task Manager open and tab back and forth to check periodically; be sure to put the game in windowed mode first, as it doesn't always respond well to alt-tab in fullscreen mode. The game can only use ~3.7 GB RAM, and a temporary memory spike above that can cause an insta-crash like you described, with no warning and maybe not even an error message.

It's also a good idea to check your in-game framerates. Bring up the cheats console (ctrl-shift-C) and enter "fps on" without quotes. A number will appear in the upper right corner of the screen, and it should never go above the refresh rate of your monitor. If it's consistently high or fluctuates wildly, you'll need to manually cap fps. This is simple, but which tool(s) to try depends on what graphics card you have.

There are so many reasons Sims 3 could crash, it's difficult to know where to start without more information. But if the issue isn't RAM or your in-game framerates, please list the world(s) you've been playing in, and any pattern you've noticed to the crashing, e.g. if it happens at the same in-game time, or when you access CAS.

You are in great hands with @puzzlezaddict to help you. In addition to watching RAM and fps numbers, and making adjustments, there are things you can change in options that help a lot. Turn off all store and on-line notifications, game spawning additional animals, occults, and celebrities, weather options (until you want something turned on manually for a bit), and, of course, memories. Watch how much your sims collect in their backpacks and keep them cleaned out regularly.

I also find two tell-tale signs that my game could crash on me. There are two compositor files that get much larger as I play. When the first compositor files gets over 100,000 in size or when the simcompositor file gets over 350,000, then it's time to save and quit and delete those files to get refreshed before reloading.

Every time I use the launcher, I get .temp files in the dcCache folder. So I delete those .tmp files before loading my game. This only works if you aren't tied to Origin with the latest patch. Other folders can be kept cleaned as much as possible too. I delete older saves, keeping only the last two of a game, I rename and delete the screenshots folder often (as these show up in the launcher and can make it more challenging to work efficiently) as well as the video folder, if you make videos.

Good luck with your game.

So I tried the FPS on and it was showing 500-510 and my refresh rate is only 60 so maybe that’s it? If it is how would I fix it? So far the ram isn’t going up too far so I don’t think that’s the problem.

The high fps alone could definitely account for the crashing, or it could be causing your hardware to overheat and your system to crash the game in response. Either way, running at 60 fps should help a lot. If you have an Nvidia graphics card, you can enable vertical sync through the built-in Control Panel, although this doesn't always work (and only ever works in fullscreen mode). This guide has good screenshots of the CP, under the first spoiler:

https://forums.thesims.com/en_US/discussion/comment/16540301/#Comment_16540301

If CP doesn't work, you can download Nvidia Inspector (free) and manually limit fps. Or, if the driver for your graphics card is new enough, you'll have the option to set a max framerate in the Control Panel, which works in either fullscreen or windowed mode. (CP > Manage 3D Settings > Max Frame Rate; set to On and limit fps to 60.)

If you have an AMD graphics card, you can try the built-in Crimson software: create a profile for Sims 3 and have a look around. (I don't know exactly what all the options look like in the new software.) If that doesn't work, you can download RivaTuner Statistics Server (also free) and manually cap fps at 60. Unlike the others, RTSS does need to be running while you play, so be sure to minimize it rather than Xing it out. You can also use it with an Nvidia card if you want.

In any case, to create the profile for Sims 3, you'll need to use TS3.exe for an Origin install, or TS3W.exe (with the W) for a disc or Steam install. If one tool doesn't work, just move on to the next one.