I think he's particularly prone to lash out when he sees criticism about unsubstantiated claims of wealth (obviously), about his business acumen, that comes from someone who had previously said nice things about him, or anything negative in the New York Times.
Whenever you see one of his many tweets about the terribly run NYT which is failing and will be out of business soon, you can count on being able to find a recently posted negative NYT article about him.