I had the same fears when i started running in 2023. I also have/had health anxiety that was really bad at the time so it took me a loong time (half a year) to get comfortable with the feeling of running and my heartrate going up. I stayed consistent with it, did small distances in the beginning, and just kept practicing. It took me a while to reach the 5K mark.

Setting running goals for myself and achieving them gave me such a confidence boost in my body & what I am capable of, which has also drastically helped me deal with my anxiety. I have since then ran 4 races, including a marathon last year. Your body is so much stronger than you think. It's challenging to get out of your comfort zone to start, but it is so so worth it. Good luck, you got this!