My 15 month old well taken care of watch just randomly stopped. Tried the reboot. Nothing. So upset.

What is the lifespan for an Apple Watch SE? It was working until about 5 o’clock when I went for a walk and I looked down to set it on outdoor walk and it was dead. Is it already been charged this morning but I tried that again and also tried to reboot and nothing. The watch gets warm when it’s on the charger. First day in 15 months I haven’t closed my rings.