It certainly is strange behaviour from your Kindle.
Did you try to reboot your Kindle or synchronize it with Amazon? Sometimes that helps.
I have another suggestion; just to rule bad indexing out:
Can you check (by random search) if the Kindle is stuck on indexing a book? That makes it unstable and empties the battery as well.
Indexing a book, or several, should not take hours. If you notice the Kindle keeps on indexing (items found by random search should be 0) ----remove the books that you loaded recently and add them one by one (check at each book if it's indexed).
If the problem is a book from Amazon; tell them and they'll reimburse you. If it's your own book--convert it in Calibre (or other) from mobi to mobi. (the format Kindle reads).
Good luck
