Did you update the recent patch? almost all generations of kindle
needed a patch update.

The latest software update for Kindle Paperwhite (6th Generation) is 5.7.3. This update automatically downloads and installs on your Kindle Paperwhite when connected wirelessly; however, you can also manually download the software and transfer the update to your device via USB cable.
https://www.amazon.ca/gp/help/customer/display.html?nodeId=201307450

Try cold reboot at a last resort.

If you want to unfreeze your Kindle or restore the factory defaults, do the following:

1. Hold the power switch to the right for 20 seconds.
2. Press the HOME button for 1 minute. Eventually you will see the screen to your right.
3. Nine times out of ten just hitting the DEL button at this point will unfreeze your machine without having to lose all your files (please note, you can replace them later but it takes time and you will lose your notes, bookmarks, and settings).
4. If that doesn't work you will have to restore the factory default settings by typing in R E S E T. As soon as you hit the T it will reset.
That's it. Please note that this is for the Kindle 3G + wifi 6 inch version.