That used to happen to me too. Not sure what it means though. However, this is a good time to either 1. use that as a dreamsigh to reming yourself that you are dreaming and thus become lucid or 2. turn around and fight your attacker. If you ask an attacker wgat his name is, he will lose his powers. Attackers represent fears and anxiety, so when you ask them to uncover themselves they disintegrate. Try it.