Hey Doc I Usually Take A Shower For About 30

Hey Doc I usually take a shower for about 30 minutes and evrything's fine for the first 15 minutes but then my heart out of no where just suddenly starts to beat very fast and even starts to pain and its very frightening why is this happening doc about six months ago I recovered from pneumonia with out proper prescibed medication can this have anything to do with this and the once in a while palpitations?