What do these symptoms mean?

For the past 4years I have awakened panicked feeling like I was choking, gasping for air. It hasnt happened since this year but now something else is going on. It always happens at night usually 1 to 2 hours after laying down, sometimes I am still awake and sometimes I am awakened. Last night it was the worst. I had a warning so I sat up in the bed, a very uncomfortable almost fear like sick feeling and I could feel my heart palpitation and on the side of my neck, this time it felt like both sides and the rhythm wasnt right. This time it was accompanied by the shakes, much stronger and lasted longer, 30 secs as opposed to 10-15. It doesnt happen everynight , sometimes once a month, once a week. I am 34.