It's recovery mode. I'll post the link to the support page, it will guide you on how to do it just make sure to follow for your specific phone as each phone is different.

https://support.apple.com/en-us/HT201263#:~:text=1%20Make%20sure%20that%20your%20Mac%20is%20up,with%20these%20steps%2C%20but%20don%27t%20...%20See%20More

Getting warm it typically normal as phones don't have fans so they disperse the heat across the device when doing hardware intensive tasks. And if you follow the steps in that article and the issue continues it could indicate an actual hardware failure.