Docs, could a healthy person develop asthma out of nowhere?

Possibly: Shortness of breath may or may not be asthma. The only way to find out is get tested and give a good history of your attacks, frequency and severity. Don't wait too long Good Luck.

No- it's a process: Though coughing and wheezing caused by "brochospasm" can occur, it is because of a situation that irritates the large airways. This will usually resolve once the irritant is removed. Asthma on the otherhand, is a process that involves bronchospasm and inflammation, which gets worse over time if left untreated. The cause is multi-factorial, but it doesn't appear from nowhere.