What just happened to me

Hi I've been sat using my phone deep in concentration and out of blue my heart stopped and gave a deep thump in my throat I'm so scared right now..... I've also been getting numb warm sebsations on top of my arms xx

have you seen a cardiologist?  From there, they may know what's next.  I'm not going to tell you it's anxiety, but it does come in many forms and symptoms..