My Kindle Paperwhite was stuck on the startup screen while resetting to its original settings.
There is no way to access the Settings screen.
In such situation, you can perform a(nother) hard reset with a computer and a USB cable.
- Create a file on the computer with the following name: DO_FACTORY_RESTORE (without extension)
- Connect Kindle to computer
- Copy the DO_FACTORY_RESTORE file to Kindle
- Eject Kindle
- Press & hold the power/lock button for 20 seconds
Kindle should restart a few times and reset to its original settings.