This happening on two gen 7 iPads for me. I find I can load and play in default mode as Steve. As soon as I login, sometimes it freezes logging in, other times it goes to loading and then freezes. I notice the resolution on the loading screen is higher when in my avatar rather than default Steve. I would try mine in lower graphics mode if I could get to settings to change it.
Installed the Xbox live app. Followed the directions. Still freezes after logging in which then causes the next startup to freeze on load.
Also tried triggering the launch of Minecraft from there Xbox live app. It does start the application, but I'd not logged in and only gets as far as having launched it myself. Nothing works with that route either.