Distorted image while booting.

Hello. For the past 3 weeks I've encountered strange, distorted image while booting. I have a MacBook Air 2018, currently running macOS Catalina 10.15.6.

Usually, booting lasted about 30 seconds, but now it takes about 2 minutes, while also presenting distorted images.

First, startup looks normally :

Then it goes:

and finally :

and then it finishes and shows my desktop. (hello, that's me and I know I have dirty screen, I promise to clean it up :) )

I tried a lot of things, like reseting SMC, NVRAM and PRAM, restoring from Time Machine, reinstalling macOS from Internet Recovery.

The only thing that worked, was safe mode. It works only for the first startup after using it, tried it several times.

Can anyone help me please?