No, it's something happening in the background, in order for the Kindle to be able to search in your books.
You can see wether all books are indexed, with random search (type whatever combination of letters , for example ' tiyhdle' ------that gives you the search-option). Then press ' search' on the right side of the line.
It starts to search--may take a while to do---you can see it by the 'spinning wheel' in the upper left corner, and then it gives you the result----should be 0, if you've not recently loaded a book.
But it's just a thought; it could well be something else. Did you get the latest update?
Otherwise: just call Amazon; twice if need be (though always friendly; their quality differs).