Hi there! My name is***** am a computer professional with over 15 years of experience with both Mac and Windows computers, phones, tablets, e-readers, and printers. It would be my pleasure to assist you with this.
This problem and many others are often the result of a "glitch" in the software.
Your Nook is likely rarely shut down, as just pushing the button puts the Nook into sleep mode. However, if you press and hold the power button for 5-10 seconds, your Nook should will pop up a box asking if you want to turn it completely off. If you tap 'Yes', it will fully turn off. Wait a minute or two and then turn it back on and see if it is running better. That may be enough to resolve your issues.
However, if you do continue to experience problems, we may need to do a factory reset. The generic steps for a Nook factory reset are listed below. This will work for most Nook models:
Please Note: A factory reset will deregister your device, removing all digital books and files, including side-loaded content. The titles you have purchased will remain in your account. It is recommended that all side-loaded content you wish to save is backed up to an SD card or computer before proceeding.
To Factory Reset Your Nook please do the following:
Please give this a try and let me know how it works for you. If this solves the problem, would you mind taking a moment to rate my service? You can give your rating by selecting the stars located on the top right of the question page. I'd really appreciate it! Without a positive rating I am not credited for my answer. If this doesn't solve the problem be sure to let me know so we can continue troubleshooting.