iphone keeps getting frozen in apps/home screen?

my phone keeps getting sort of stuck in apps and last night it got stuck on the home screen as well. the only part of the screen that is responsive is the bottom part where you’d usually drag to return to the home screen/view your open apps, but it doesn’t actually do that. it drags, but it doesn’t change menus. just locking the screen and turning it back on helps, but it’s been happening increasingly frequently over the past 3(?) days and it’s very inconvenient. does anyone know why it’s doing this and how i can permanently fix it? thanks