Try a normal restart first

If macOS responds, choose Apple menu > Restart and save open documents. You may disable reopening windows for a cleaner startup.

If it does not respond

Hold the power button until the Mac turns off only when necessary. Unsaved changes may be lost. Wait until shutdown is complete before closing a laptop lid.

Do not jump straight to reinstalling

A question mark, prohibited symbol or stuck progress bar can have different causes. Do not erase the disk or reinstall macOS before checking the right recovery steps and backing up when possible.