There is an issue with the way Accessibility features work on macOS with MATLAB at this time.
You can follow these steps:
Go to System Preferences > Security & Privacy > Privacy > Accessibility. This list shows all the applications that you've given permission to use the Accessibility API. One of these applications is triggering the bug in MATLAB and causing it to hang.
You'll need to use a process of elimination to determine which application is preventing MATLAB from starting. It is likely to be an app that gets and sets information about other application windows.