To get redirected to a random Wikidata item without "instance of" (P31) or "subclass of" (P279):

http://tools.wmflabs.org/wikidata-todo/random_item_without_instance.php?run=1

To ensure that the item has a link to a Wiki(m|p)edia, e.g. "enwiki":

http://tools.wmflabs.org/wikidata-todo/random_item_without_instance.php?run=1&wiki=enwiki


Tip: Drag one of the above links into your bookmarks for easy "new random item"; you can subsequently change the wiki by editing the bookmark.