Non productive cough when nervous. how to supress?

Your doctor can help: Safe, and usually low dose, use of serotonin-active antidepressants, or possibly the medication Buspirone can be very helpful for this problem. It might be a form of obsessive compulsive disorder, however, which may require more in-depth treatment.

This isn't that : Uncommon. Breath in slowly ; deeply through your nostrils. Fill your lungs with air (but not to the point of discomfort). Hold for a count of five then slowly begin to exhale through an open mouth. Repeat at least 12 times, longer if you need to.