iphone 14 screen glitching

i have bought iphone 14 recently. its battery health initially was 99% but after a week it dropped to 98%. after using it properly, i have noticed that the screen of it is glitching on app switches and normally it does. i have turned the automatic brightness off, after that it has reduced a bit. but the issue is persisting. i have got my phone checked after buying, all other shops said its water pack and never opened for any repairs. what is the reason of the screen glitch?