My nexus 5x has a clicking sound when i’m shake it.
It is ok, not ok?
Well, that doesn’t sound ideal! Perhaps something has become lose internally which isn’t good. Not sure what you can do about it – if it’s still under warranty I suppose you could phone them up and see what they suggest. But I can’t imagine they are going to offer a replacement unless something isn’t actually working.
If it is out of warranty then there is not much you can do really. Keep using it and hope it hangs on until the 2016 Nexus Phones are released!