I am a smoker and when coughing hard I frequently get light headed and stay that way for 2-15 seconds, 5-8 times a day.
Coughing creates a vasovagal reaction.
Vasovagal reaction: A reflex of the involuntary nervous system that causes the heart to slow down (bradycardia) and that, at the same time, affects the nerves to the blood vessels in the legs permitting those vessels to dilate (widen). As a result the heart puts out less blood, the blood pressure drops, and what blood is circulating tends to go into the legs rather than to the head. The brain is deprived of oxygen and gives a transient sensation of lightheadedness.
Is this something that is dangerous or is it normal?
It is not dangerous and is quite a normal sensation. However, it is the coughing itself that is not ok. Your smoking may be causing you a chronic bronchitis which is your first step in the process of developing emphysema. You would do well to look into smoking cessation.