Kindle fire HD keeps shutting down?
Every time i try to unlock it, it shuts down
Remove the cover/case. I experienced this on my nexus 7.
Have you tried to reboot the device? It should solve such kind of problem. Here's some details on how to reboot the device, as well as suggestion to other common issues:
Try to charge the device fully as well. If problem persists, contact Amazon and see if they can offer any help.