The new 10.15.3 is not installing when I restart. Just reboots back to the Systems screen.
The new update for Mac OS Catalina is not installing. It just goes in a loop when rebooting and never installs.
MacBook Pro 13", macOS 10.15
Boot into Safe Mode (Use Safe Mode to isoloate issues with your Mac and Playing Safe: what does Safe Mode do?) and try installing from there.
NOTE: Safe Mode boot can take up to 10 minutes as it's doing some system cache cleaning, volume verifying and directory repairing.