If you accidentally queue up multiple hibernate or sleep commands, then your computer might end up in a loop where it constantly turns off by it self. Here are some things you can try.
Close the app completely on your phone (if you pressed the button multiple times then these actions may end up getting "queued")
Restart your computer (hold the power-on button down so that your computer restarts completely)
Start your computer in safe-mode. Refer to instructions for your specific computer.