My phone doesn't boot (red led)

My phone started shutting down by itself many times during the day and also it became very hot.

So I decided to recover it through the Sony companion app. I did it many times because it never became usable but it turned black and now it doesn't show anything on the display and it isn't recognized anymore by Sony companion because it doesn't boot in download mode.

It can also be that it is dead in the middle of a recover done through Sony companion.

Now, if I connect it to the charger (or to the pc), it shows the red led for a while and it turns off. It seems that the phone “turns on internally” and then it turns off the red led.

If someone knows what is the problem and can help me, thanks.