@BongoMan1235 While your Mac meets the minimum requirements for 64-bit Sims 3, I think your graphics options might be a bit too high, especially with only 8 GB RAM installed and no dedicated graphics card with its own video memory. But the 15-minute interval before this happens seems a bit weird to me—I'd expect more variability, depending on what lot you were playing on and other random details. if this were merely a hardware issue.
The first thing to try is playing Sims 3 with nothing else running in the background. Restart your computer and don't open any other apps. Put Origin into offline mode before pressing Play, and disable the Origin in-game overlay, under Application Settings > Origin in-game.
If the same thing happens, repeat the above, including restarting your computer, except this time, disable the wifi after taking Origin offline and before launching Sims 3.
Let me know whether this makes any difference, not only if the glitch doesn't happen but if it happens somewhat later.
If the above makes no difference, or it only postpones the glitch, try turning down the graphics settings to the minimum. Disable Advanced Rendering too. Do so at the Main Menu, then quit to desktop (and restart your computer for good measure) before loading a save. The point is not to play this way going forward but to find out whether any changes help. If they do, you can raise the settings again, one or two at a time, and see whether the glitch comes back.