8 mnths old baby girl making wheezing sound (difficulty breathing)for 15secs somtimes in a day no wheezing sound when sleeping?

See a doctor. There are several possible causes and more information is needed to offer advice. Your child needs to be examined.
Foreign body?reflux? Seek medical attention. A chest xray may be useful to rule out an accidentally ingested foreign body.The other common cause for this symptom is acid reflux from the stomach with micro aspiration to the trachea and bronchial tree. A pediatrician could supervise a trial with oral antacids , if the chest x ray is negative.