Thanks for the reply. This has happened before, but I had a break from playing The Sims 3. Yesterday I played for an hour in the Appaloosa Plains world, and the screen froze when my Sim was in the park.
As I mentioned, I could still move the cursor and hear that I was clicking on things, so when I clicked to close The Sims 3, I could hear that the save window appeared on the screen. Even though I couldn’t see it, I clicked from memory where the “Save” option is, and I managed to save the game.
I closed the game and then launched it again several times, and each time it started from the saved moment and immediately froze on the screen. So unfortunately it wasn't for a short amount of time. I know that the game doesn’t run smoothly on macOS, I was fine with minor lags. However, at that moment the game completely froze.