I was sleeping and then woke up suddenly with a very fast heart rate. it was back to normal within 3-5 minutes. was this heart related or panic attack?

Tachycardia: Brief episode of heart racing can come on with activation of your flight or freight mechanism ( sympathetic nervous system) it's ok to have this racing of ur heart provided is sporadic and back to normal when situation improves . Panic attacks can accompany heart racing too. If having difficulties during the day especially headaches and somnolence may want to check for sleep apnea. Good luck.