My phone keeps restarting. All my contacts and messages deleted. I can't message. And I can't set a wallpaper. What do I do?

About 3 days ago my phone said it was sending a message but never fully sent yet the Person I was messaging got it and it still says it's sending. So I restarted it and now my phone keeps restarting on its own, I can't open many apps. I deleted a lot of stuff to clear storage. I can't set a wallpaper and it deleted every single one of my messages and contacts. I don't know what to do