Why is Mac mini taking a long time to boot up?

Question

macOS

OS version: macOS High Sierra 10.13.3 Mac
version: Mac mini (Late 2012), HDD replaced with SSD, RAM increased to 16 gigs.
The sequence of actions is as follows: I press the power button, the power-up sound sounds, nothing appears on the screen for about 3 minutes, just a black screen (it seems like the monitor is not turned on at all at this moment), then a screen with a loading bar appears for a couple of seconds and immediately enters system.
The problem itself has been around for a long time, so remember what was installed there, etc. it won’t work anymore, but before it didn’t cause such inconvenience because it loaded faster, but it seems that every day a second is added to the load and it has already reached a completely uncomfortable 3 minutes.
What I already did:

• I checked the login objects, everything is as it should be, nothing superfluous or something that I don’t know
  
• Reset PRAM, SMC
  
• Cleaned the system with Onyx
  
• I checked the fullness of the memory, more than 50% of the disk is free
  

Unfortunately, none of the above helped.
There is also a suspicion that the system cannot save some settings and, after a reboot, resets them to those that he remembered a long time ago. For example, automatic folding of login objects does not work, iCloud login fails every time and does not remember the position of windows in the application. There may be something else, but I didn't notice.
It feels like something is littering the system every time. Or some kind of SSD problem (I don’t remember seeing similar problems before the replacement), plus no one has similar problems on other exactly the same machines with the same SSD.

Answer 1

I go to sleep for a very long time (only after the update

Answer 2

Open Terminal, type top, hit enter. Show processes and resources.
Open Console and see system log, or something like that. There, loading errors are usually displayed. Except for deep hardware issues.

Answer 3

The same situation and such a computer. Nothing helps, and Apple does not respond to requests.