Do you by any chance have the laptop on a stack of MacBooks? Just this week I had this same problem (boots halfway and then goes to sleep before showing login screen) and found out that it’s due to the magnets on the laptop beneath. Those magnets trigger the sensor on the upper laptop, making it think the lid is closed. Of course, nothing you do will get the screen to wake when the laptop thinks the screen is shut.
Solution: take the laptop off the stack! Worked like a charm for me, let me know if it works for you!