by any chance

Used as a polite emphasis to a request or question.

Would you by any chance happen to know where the subway is from here?

Let me know if you should come across a copy of that book by any chance.

Are you in love with him, by any chance?

可以说 Do you by any chance have any idea what time it is?

By any chance如果用在句首，通常应该有逗号。但口语中主要用语调表示而不一定有停顿，所以有时对口语作书面整理时就没有用逗号。