Fans turning on when in Sleep mode or the lid is closed

Hi everyone,

So the issue with my Mac which I couldn't figure out what causes it: when i put it in sleep mode or just close the lid the Mac still runs just with blackened screen. Also the fans randomly turns on and start spinning on max RPM.

I don't understand why the Mac doesn't hibernate like a Windows notebook and why the fans starts spinning up when it's not even hot or something.

Does anyone know what could be the issue? Tried the PRAM and SMC reset several times but doesn't seem to solve this.