I noticed a couple days ago my HA instance was not available and returns una couple minutes from a reboot.
I was seeing this every day in different times since then but when I check the logs only shows me the current (new) session. So I can not find the culprit.
The only thing I installed lately was Adb bridge.
How can I check the “last will” log in this case?
Check your power supply. Are you using an RPi?
Good point, yes is a Rpi 3b+ with the original power supply maybe is dying. Any 2A or more is suitable?
2.5 amp minimum…
And the genuine one is 5.1V. I have had best results supplying 5.5V to the power pins on the GPIO connectors.
The 3b+ is probably the most fussy of all Pis when it comes to power.
This could also be an indication of imminent SD card failure. Take a snapshot… 
hello! i change the power supply and the sd to a external SSD. Everything was fine and i notice right now the server is offline, i can’t do SSH to it or even the 4357 port. It’s like blocked, again, and when return online i have nothing on the logs to check whats going on.
The SSD have the lights On like “writing” and the ethernet port blinks too.