My mare has a cold right now. She does that I just let her cough it out. She just needs time. I'd guess your horse has a warm up cough but maybe call her vet and ask if they should come out? Are you in the open or a dirt arena?
you probably need to see a vet! it could be anything. but i know that watermelon helps!
She could have asthma? There was a horse at one of my older barns that had this problem, and asthma was the reason. I would check with the vet.
How frequently do you run her? After a lot of exertion(if the horse doesn't work that hard regularly), it can get things running in the horses sinuses.
Your horses lungs might not be strong enough either. Do you do a lot of cardio with her?
Either way, I agree with Adeline, you should check with the vet just to be safe.
No not usually, just after running her for like 1min, then I slow her down to a walk and continue walking but she coughs about 4 times
Does she cough usually? If she doesn't, I think you should call a vet :)