Does start up, can't log in

So as the title says: I can't login, it will start but I can't login. I get the spinning wheel and the mouse turns into our rainbow spinning wheel and they just kept spinning until I shut it down after more than a half hour.

What happened: I was working and suddenly out of the blue it reboots and after the start sounds it reboots again and after that I wasn't able to log in anymore.

This is my last hope since I tried everything I could find, things like:
- Safe modes
- Disk utility/repair
- SMC reboot
- cmd r
- fsck -fy
- PRAM reset
- and many more

but nothing worked, so please I need some help!!

Thanks