If feels like the feeling you feel if someone was to jump out from behind something and scare the **** out of you, or the feeling when a cop turns his lights on you to pull you over, or such feeling like that, hard forceful heartbeat, not fast, kinda like shocked into a slow hard heartbeat, fluttering feeling in chest
, mild left side chest pain
, and short of breath. What could cause this in the middle of the night and wake me from a sleep? Could it be potentially dangerous?