The best tutorial to fix mac pro bottom screen shake from time to time
I found this tutorial on apple official website,you just need to reset the System Management Controller (SMC)
https://support.apple.com/en-us/HT201295
These are my steps:
1. Choose Apple menu > Shut Down.
2. After your Mac shuts down, press Shift-Control-Option on the left side of the built-in keyboard, then press the power button at the same time. Hold these keys and the power button for 10 seconds. If you have a MacBook Pro with Touch ID, the Touch ID button is also the power button.
3. Release all keys.
4. Press the power button again to turn on your Mac.