What Causes Irregular Beating In Forearm Area?

Hi i am a 21 year old female and for some reason the past few days i have noticed that when my left arm has a little pressure on it that all of a sudden my left forearm area right next to my ulnar artery starts beating very irregular and you can see it beating if you are looking at my arm with out touching it. But when i relieve any pressure thats on it it goes away (when i mean pressure my elbow is just on the table and my hang is elevated to my face.) what can this mean. Oh and also at the same time this is happening i auscultated my carotid and it was normal beats