A disconcerting habit of narcissists: doing good deeds for show

I don't know how common this habit is among the most narcissistic individuals. But it seems that there are certain types of narcissists who are more likely to do good deeds, not because they are truly altruistic, but to show others how supposedly kinder they are. And it's a disconcerting habit, considering that highly self-centered individuals are expected to only take actions that benefit themselves, also in the sense that they maximize their own physical and emotional well-being. But in the case of the narcissistic type who likes to pose as morally superior, this performance may serve precisely to stroke their gigantic ego.