Finder automatic opening at start

Boot into Safe Mode according to Start up your Mac in safe mode - Apple Support and test to see if the problem persists. Reboot normally and test again.

NOTE: Safe Mode boot can take up to nearly twice as long as a normal boot as it's doing the following; 

• Verifies your startup disk and attempts to repair directory issues, if needed

• Loads only required kernel extensions (prevents 3rd party kernel/extensions from loading)

• Prevents Startup Items and Login Items from opening automatically

• Disables user-installed fonts 

• Deletes font caches, kernel cache, and other system cache files

The Finder should be open all the time it is the background app that

keeps your mac running, without it nothing would happen.

If you mean a Finder window opens when you start your mac then make sure all Finder windows are closed

before you set your mac to Sleep or Shut Down.

Duel89 wrote:

Hi, every time the mac starts, finder open, even if closed in the previous session. Do you know how to avoid it?

Yes, what I meant is the Finder window. It is from Mac OS X Tiger that I have never encountered this behavior, the window always opens at startup even if closed to shutdown. I suppose some other application that starts at the start, also opens the Finder window.

How is this an issue?

Get to know the Finder on your Mac

https://support.apple.com/en-us/HT201732

See and organize your files in the Finder on Mac - Apple ...

https://support.apple.com/guide/mac-help/finder-mchlp2605/mac

Support for OS X Tiger ended in 2009

Just about all mac users would be perplexed if their mac started without the Finder.

What Eau Rouge said about Finder windows, which I also believe is what you meant.

But just to be thorough, one can use a mac without the Finder. The Finder can be quit and other applications will continue to work. One could have a script running on login that quits the Finder if that is what you want; but the fact that you asked strongly suggests that you don’t want that.