My phone is hot and is not on again

Most likely the cause of the heat issue is a bad, or failing battery. That is the most common cause of heating up. It is possible that the battery got hot enough to destroy itself, or even the internal components of the phone. I would check the battery. If it is bad, replace it. It is also possible, but unlikely if your phone is not showing any physical damage, that the battery ruptured and caught fire (oxidized). This will usually destroy the phone as well, but not 100% of the time. I actually had a battery in an iPhone do that, and I managed to get the phone working again by simply replacing the battery and the display assembly (this was in an iPhone 6s), so I was lucky and had no damage to the logic board or frame.