What should you do if you felt uncomfortable and out of breath?

When someone feeling out of breath, that means the oxygen demand is higher than the oxygen supplied. It is normal when you do moderate-high intensity exercise.
The action of you should do to relieve it would be decreasing the oxygen demand by lowering your physical activity. Try to slow down if you are running or take rest by sitting down for a moment.
If the problem persists or happened multiple times, you should talk to your doctor.

The answer is sensory neruon