how to fix very slow startup on MAC desktop running Ventura 13

If it is an Intel-based Mac, try starting up in Verbose mode (cmd-V on restart).

That will stream lines of information as it starts up. If you can identify lines where it stops for a long period of time, that might give some clue as to the problem.

Starting up in Safe Mode may help as it clears some system caches. Restart normally after.

Have you installed and run any "cleaning", "optimizing", "speed-up", anti-virus or VPN apps on your Mac?

Download and run Etrecheck. Be sure to give it Full Disk access before running.

Copy and paste the results into your reply. Etrecheck is a diagnostic tool that was developed by one of the most respected users here in the ASC and recommended by Apple Support  to provide a snapshot of the system and help identify the more obvious culprits that can adversely affect a Mac's performance.

Copy the report

and use the Additional Text button to paste the report in your reply.

Then we can evaluate the report to see if we can determine the cause of the problem.

munnsterspain wrote:

how to fix very slow startup on MAC desktop running Ventura 13

The current stable release of Ventura including bug fixes, security updates is macOS Ventura 13.4.1 —I would start there.

Keep your Mac up to date - Apple Support

Keep your Mac up to date - Apple Support

Also, you might check how many startup files you have set to be opened when the Mac is turned on. If you have a lot of them, they can and will eat up a lot of time.