I get a phlegmy couch when running, should i be worried? am in generally good health and don't smoke.

It depends: Note the color of the phlegm. If it is clear white, there is no serious problem. But if it is yellow or green color it could mean there is some element of infection or bronchitis. Unless you have shortness of breath or worsening of these symptoms, i would not worry about it and ignore it for now.

Exercise induced: Some people get exercised induced cough and wheezing(exercised induced asthma) but usually the cough isn't overly phlegmy. If you're fine otherwise it could be a form of exercised induced asthma without the wheeze. Asthma type inhalers used just before running may help. See your pcp for evaluation.