Q: iphone shuts off during "restore from backup". normal?

Iphone 5. very latest version of ios 8.

Att provided me instructions to unlock my iphone.

1. connect to itunes

2. back up iphone

3. restore from back up

when i restore from back up, my phone shuts off. is that supposed to happen? I turn it back on and I get a white screen and it says "slide to upgrade". i do that and i am back in and everything looks the same as before.