If your Firestick is stuck and frozen on an application or during initial load, most of the times, a soft reboot can sort the issue.
A soft reboot won't cause any data loss and will simply reload the device. This can easily be done using a shortcut of two buttons on the remote controller.
1-Click and hold Play/Pause button the the remote and while holding it, hold the Select button (the center button)
2-After 3 seconds, "Your Fire TV Stick is Powering Off" should appear
3-Once the device goes into the reboot, you can release those buttons
4-The device should boot up quickly and the freezing problem fixed
While that usually works, if the freezing issue is something which is happening often on your device, maybe it is time to do a Factory Reset. Resetting a Firestick to factory defaults will remove all your applications, files and personal data but it will free up space and brings the device back to the default, optimized settings. A step by step guide on resetting Firestick to factory defaults available here.
Any questions? post it on WDS Community Forum and let us help you.