Stick drift. Happened to me on my Rift S a while back, then I broke my controller trying to fix it. If you go into the game settings and change it to auto run, it will help, so you won't be clicking to sprint every time and it should remain even if the stick thinks it was centered briefly.
#Unable to run properly
keen umbra
noble hinge
Try cleaning the inside of your joystick. The receiver may be dirty. I had the same issue on my quest 2 and you can try to clean it out