My resting heart rate is about 65 bpm, normal for a 17 year old, but I walked up the stairs and my hr jumped to 165. I get jumps like this frequently when I stand up or walk across a room. I don’t feel particularly out of breath, but I do feel dizzy. It takes about 2-3 minutes for it to go back to normal. This makes it nearly impossible for me to exercise because I get dizzy so rapidly.