Why does my 4 month old get sob &retract when breathing in am & gets better throughout day? Also seems to get sob with activity or position change?

4 months old breathi. A 4 months old with these symptoms need to be evaluated by your pediatrician as his symptoms may be due to lung condition like bronchioliti, asthma or there is possibility heart disese, which is less likely as he would have been discovered with a heart murmue by noe during routine visits with pediatrician.So make an appt.With your pediatrician and have him examined asap.