Make sure to disconnect all external devices in case one of them is causing a problem.
Try booting into Safe Mode to see if that lets you to finish booting. If so, then you most likely have an issue with some third party software.
Try booting into Recovery Mode to run Disk Utility First Aid on the hidden Container. 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.
Try performing a PRAM Reset (hold the PRAM Reset for two chimes if possible).
Reinstall macOS over top of itself. I've encountered a few instances recently where some of these boot loops require reinstalling macOS over top of itself. This should not affect the data on the internal SSD, but you should make sure to have a good backup anyway (hopefully you already have a backup since there are a lot of new ways to permanently lose access to the data on the internal SSD of these 2018+ Macs due to all the new hardware, software, and security changes).
Lastly, you may need to try a DFU firmware Revive which resets the T2 security chip & system firmware.