freezing ipad

using it, sometimes it turns the screen black with the loading circle in the centre and closes all the application in use; two seconds and i am on the lock screen and can start again from there. This happens when i use notability but also when i’m watching something in pip mode. I have an ipad pro 2018 and it’s not great. I already contacted apple support but can’t tell me anything but uninstall notability and re try, all parameters were optimal. I think the problem is ipados