MacBook Pro 14 inch restart after I login and type password for my username.
Mac opens up up to login screen and when I type password instead of taking me to home screen. It restarts again.
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Try booting into Safe Mode. Does this work, or does it also automatically reboot again? If you can boot into Safe Mode, then most likely you have some third party software installed which is causing the problem.
Boot into Recovery Mode. Quit the macOS installer. Launch the Terminal app from the Utilities menu on the menu bar. Execute the following command to clear the NVRAM (safe for M-series Macs....press the "Return" key to execute the command):
nvram -c
You may see one or even several "not permitted" notices for not being able to clear the Computer Name & other related items. That is Ok as long as there is no other error related to the "nvram" command. Reboot the laptop to see if it will boot normally.
Try running the Apple Diagnostics to see if any hardware issues are detected.
Disconnect all external devices in case one of them is causing a problem.
Run Disk Utility First Aid on the hidden Container while booted into Recovery Mode. Within Disk Utility you will need to click "View" and select "Show All Devices" before the hidden Container appears on the left pane of Disk Utility. Even if First Aid says everything is "Ok", click "Show Details" and scroll through the report to see if any unfixed errors are listed. If there are errors, then run First Aid again until they are gone. If after several attempts the errors remain, then most likely they cannot be repaired. Reboot to see if it made any difference.
Boot into Recovery Mode again, but this time reinstall macOS over top of itself. Hopefully the installer is for the same version of macOS that you have been using so you can retain the same version of macOS. I have had to do this reinstall on two of my organization's Macs for reboot loops on macOS which were caused by a macOS bug. This should not affect any data or apps (theoretically).
Out of curiosity, what happened just before you got into this boot loop?
What version of macOS were you using?
What is the exact model of your Mac? You can get this information by entering the system serial number on the check coverage page here:
Check Your Service and Support Coverage - Apple Support