Why is the device being really hot and shutting down?

It certainly seems like an issue with the machine overheating. I’d recommend taking the machine apart with help from this guide: Acer Iconia W3-810 Back Panel Replacement and ridding the device from dust using compressed air as most of the time a mass of dust build up can cause a system to overheat. If this machine has a fan i’d also recommend taking that apart and carefully clean it using cotton buds and cleaning alcohol.

While the machine is apart, you will be able to determine whether you will need a new cooler for the CPU, but most likely new thermal paste will suffice. Unfortunately I do not have this device and am unable to locate where the CPU is but if you find it, i’d also recommend adding new thermal paste to it.

I hope this helps :)