While playing volleyball tonight I got a random sudden feeling that my heart was quivering/beating a million miles per minute. Placing my hand over my heart I could feel a vibrating/shaking pulse close to 200bpm but my carotid pulse felt strong and around 90bpm. I have had this happen several times randomly and become very naseous and light headed and almost feel like I have a lump in my throat. When I was younger I passed out a few times from it.