Alexander correctly noted that this is due to increased blood supply to the spleen, that is, the rapidly accelerating blood overflows the organs, and they, in turn, press on others, creating pain. To avoid this, you just need to do a warm-up, then the body will understand that there is a load and everything should be in order :)
A person captures a lot of air while running. You need to learn how to breathe correctly and exhale excess air. Stop and exhale as we were taught at school - deep exhalation.