I sometimes get a light dry cough but its only at night usually and i'm usually fine when i wake up next morning. what is this?

No cause for alarm: 18 year old male asks, "I sometimes get a light cough but its only at night usually and I'm usually fine when I wake up next morning. What is this?" Could be a number of things like; Allergies with Post Nasal drips, sleeping with direct fan or air conditioner blowing directly at the person. However if one is fine in the morning, there is probably no cause for alarm.