Try booting to Safe Mode. The boot up takes minutes.
How to use safe mode on your Mac - Apple Support
Next if you can, open Activity Monitor and stop the update process running If you can then try deleting the Monterey installer that is in the Applications folder. If so then restart and again boot to Safe Mode and download the Monterey installer
Do you have enough free disk space?
If upgrading from macOS Sierra or later, your Mac needs 26GB of available storage to upgrade. If upgrading from an earlier release, your Mac needs up to 44GB of available storage.
Also uninstall any antivirus and "cleaning" apps before trying installing again.
Further, you need an Apple disk installed to upgrade to Monterey since the upgrade includes an update to the Mac's firmware. That update looks for an Apple disk and write to the dick to do the firmware update. The install will terminate or freese if no Apple disk.
Do you have Fusion drive? Some uses have problems upgrading Macs with Fusion drives.