to blow hot and cold 出尔反尔（成语）

英文释义

(IDIOM) To vacillate; to change one's opinion in a weak, indecisive way.

例句

The boss often blows hot and cold, depending on his mood, and so no one can predict his decisions on anything.

这位老板总是出尔反尔，一切取决于他的情绪，所以没人能预测他的任何决定。