The cursor continuously gets bigger when I shake it.
That’s an accessibility feature. If you don’t want it you can turn it off in System Settings => Accessibility => Shake Cursor
Thank you, that’s been bugging me for a while.
Additional tip:
If you want a way to find a missing mouse that’s different from the “Shake mouse” feature you’ve just turned off here. You can go to “System Settings” → “Window Management” → “Desktop Effects”, check the “Track Mouse” and select its config menu at right and set a key combo. I have mine set to “Ctrl” and “Meta”, when I press those the mouse is highlighted with a moving circular symbol. I like this better than the shake mouse since it’s difficult to trigger accidentally