The manual shutdown is not good unless you have your power switch setup in your BIOS to wait 4 seconds while it does some things.
Sometimes there is a long display of the black screen after the windows scrolling green dashes screen. You may should have waited but if it takes more than 10 minutes.....oh well.
This simple thing has brought me back before after a power failure made my reboot do as you are describing.
Disconnect all peripherals. All you want connected is the main hard drive, display, mouse and keyboard. No thumb drives, external drives, nada, zilch. Then attempt a boot.