Getting up at 1:30 am

I just got up from a deep sleep. Before I used to sleep very well and get up at 7 or even 8. But now I am getting up so early. I feel palpitations and worry that my bp will be high.I am trying deep breathing and distraction methods like writing in the journal. I am still not understanding why I get this palpitations.  I have not worried about anything yesterday but still feel sudden palpitations. I think I have a panic disorder. How shall I conquer it. My goal is to get rid of palpitations entirely. Before I was doing very well but for the last few months I am going through them everyday. I am just confused as to why this is happening to me. It is so hard to get rid of it. While writing I feel them less but feel my left arm very cold. I know it is not not my heart because I did a stress test recently and it came out ok. My doctor says I don't have heart problems. So I am going think positive and go through it patiently. Any suggestions will be helpful?