Ubuntu 18.04 and nVidia. Stuck after boot

I'm installing Ubuntu 18.04 on my notebook.

When i boot live from USB everything works fine. Then i start installation progress. And everything it's okay.

After rebooting, i get stuck just after I insert login data.
Somethimes before, sometimes after. It looks like a graphical issue.

I looked for a solution, but everything tried didn't work.
Any hint?

Thank you.

EDIT:

Ubuntu gets stuck at boot screen (freeze, not black) after attempting brightness fix for NVIDIA card

Ubuntu freezes during boot

These solution didn't work. :(

I found a solution on Ubuntu Forums.

These were the steps to solve the issue (post #3).

1. Turn on the laptop and press shift or esc during boot to show the GRUB menu



2. Press e and edit the line starting with linux adding nouveau.modeset=0


3. Press F10 to boot


4. Once logged in successfully, go to Activities (top left corner) > Drivers and install suggested nvidia driver.

After these steps everything works perfectly.

I have no idea why it worked. I understand that missing drivers where causing the issue, but can someone elaborate so I can completely understand why this solution actually worked?

The solution was proposed for Ubuntu 16.04. I had ubuntu 16.04 and worked like a charm on my laptop, but Ubuntu 18.04 introduced the same issue. Why?