there’s no rhyme or reason to/for something | without rhyme or reason
if there is no rhyme or reason to something or it happens without rhyme or reason, it happens in a way that cannot be easily explained or understood毫无道理；无规律可循；莫名其妙
Suddenly, without rhyme or reason, his mood changed.突然，莫名其妙，他的心情变了。
There's no rhyme or reason to the new opening hours.新的营业时间毫无道理。