Hi, I'm Nathan.Sorry to hear that you're having trouble, but I'll do my best to help you. Please give me a few moments to review your details here.
This symptom can indicate several possible issues: an internal hardware failure, a low/faulty battery, or just a simple memory/firmware glitch.
The first step here will be to attempt to reboot the kindle. This is done by pressing/sliding and holding the power button for 20+ seconds, or until the screen flashes (usually with an image of a tree), then release. Give the kindle about a minute to start back up, and let me know if the problem persists, we can then try some further steps, up to and including the battery. If it comes to that, I can help you with parts and instructions too.
Do you still have it plugged in?
Please unplug it before doing the reset.