Apple Watch series 3

Very Hot is an indication of a hardware problem. Your profile says Series 4 which is still in warranty, so Stop trying to charge it, and Contact Support (link) to arrange getting it checked by Apple.

OK that’s bad luck, but I still suspect a battery failure. The advice remains the same, stop trying to charge it before the battery swells and bursts the screen from the case, and get it checked by Apple. If the watch is undamaged you should be able to get battery service at a reasonable cost (from memory around $79 in USA, similar elsewhere)