Translation:Sorry, I have a question.
It happens all the time. If a teacher or professor is about to move on to another topic, a student might apologize for slowing down the lesson by asking a question. The teacher or other students might be annoyed by the interruption if time is limited. I've seen professors tell a student they are not going over that topic again and to meet them after class.
In Chinese this is a polite way to ask a question, because when you ask a question you are "inconveniencing" them, even if you really aren't. You are showing the person you are addressing respect by apologising for bothering them even so little as to interrupt their train of thought. It's effectivly the same as saying "excuse me" in English.