They've heard them all before. Falling asleep or reading during a lecture, consistently coming late to or leaving early from class, and talking to a classmate are insulting and offensive to an instructor. If you are too tired to stay awake, don't attend class. If you are discourteous in class, instructors will be much less likely to go out of their way to help you. Put yourself in their position, and imagine what it is like to stand in front of a group of 100-200 students who are sleeping, talking, or otherwise uninvolved in the class.
Many students find themselves anxious and tongue-tied when needing to talk with a professor.
Here are some suggestions about how to talk with your instructor. But, check it out to be sure. If you make an office appointment, show up on time. If you miss an appointment, apologize in person and reschedule. Adopt the attitude that your professor wants to help you .