Galaxy A20

I use my Galaxy A20 to watch facebook live triathlons, movies, , the phone sits between my aero bars. Does not move . Last night was checking out free version of Swift , after few mins the screen was flipping every 10 seconds, never ever has done that . Don’t want to get the monthly membership if this is a issue, not interested in using a tablet or TV or PC. I am used to my small cell phone sitting in-between aero bars .