A phone turning on and off,, consuming battery too first and warming,,what can be it's problem?

 

Too many background apps.

Weak battery.

Too many radios on (e.g Bluetooth, WiFi).

 

I'll go with bad battery too.

 

I have found my phone plays up like that when there is crud in the USB socket. It may cause leakage that makes the phone switch to charging mode or something like that.
Check for lint or other dirt there, and clean it out carefully with an insulated thin probe, metho and compressed air.

 

I used to have a cheap android smartphone which exhibited all of the above... Lobbed it in the bin and got a samgsung… Not promoting samgsung, but problem solved..