Once in a while, I have these weird palpitations (I m not quite sure if that s the correct term) either in my left arm or in my right thigh. It feels annoying, and I can actually see my arm or thigh pumping regularly (looks like huge muscle spasms, but doesn t feel like it)(probably to my heartbeat). These episodes are usually about 10 minutes long, and happen 5-6 times per day. I am a 17 years old male. What is that, and what can be the cause?