What Causes Palpitations While Suffering From Anxiety?

Hi, my name is Max I m 24 iv been dealing with anxiety/stress for about 5 years. Originally saw my doc and have went to er for a racing heart/ palpitations. Over the last few years I have had a few ekgs, an echocardiogram and a 24 hour holtor monitor. All came back fine. So I feel now that most my symptoms are from stress, however part of me is curious if something still might be wrong. With the exception of my first ekg, i do not recall having symptoms during my other tests which leaves me wondering if there might be arrhythmia or somthing they wouldn t be able to see unless I was having symptoms during the test. At night when lying in bed I will have a normal resting hr but when I move or turn sometimes it will speed up for no reason then after anywhere from 4-10 seconds it will go back to normal speed usually after I take a decent breath. I don t feel ill when this happens, I feel fine it s just noticing that this happens makes me feel anxious that something is wrong. Is this in anyway normal? Should I be concerned? Or am I overreacting. Thank you for reading.