Mac Mini won't start up + no chime + vent noise

I have a 2012 Mac Mini and its had some issues before, where the screen freezes and it either restarts automatically or it just stays frozen, with rectangles of noise appearing all over the screen.

I sent it to repair at the authorized service here in São Paulo but they told me they hadn't detected any issues and gave it back to me, and it was working fine (until now, a few mnths later). I had the same issues a few times today, and finally, now it just won't start up.. i managed to start it up with option+D but then it froze again, and now it doesn't chime, the light turns on but it just doesn't start up, and the ventilator starts a gradual hum that remains quite strong after a minute.

Howver, this vent sound only starts after a minute or two..

Any help would be appreciated, thanks!