Is it normal for a 16 year old to have heart burn?

No: Heartburn is one of the tell-tale symptoms of gerd (gastroesophageal reflux disease). I'd start with some dietary changes (smaller more frequent meals, less acidic foods, give up caffeine, soda, cigarettes and alcohol, which can aggravate reflux). You may benefit from elevating the head of your bed when you sleep. You may want to try over the counter meds for reflux. If all else fails, see a dr.

Pretty common: Much of the heartburn in teens is diet & lifestyle related. Products with caffeine or caffeine like substances (chocolate, colas, energy drinks) relax the upper stomach entrance & allow easier backwash of stomach acid. Napping after a meal adds to it. Spicy foods, etc. all add up. Avoiding the triggering foods & not laying down for at least an hour after meals can help. Some need short term meds.