Had something similar to this. The laptop (Lenovo Yoga 930) I was troubleshooting could shut down when the power button was pressed long enough and it would boot up properly loading Windows etc. when the AC power is disconnected. But whenever you restart, the laptop hangs on the same screen when the AC power is connected. What I did to fix it was enable the feature in the BIOS to allow installing older BIOS versions. Enabled BIOS Backflash I think it is called. Because the machine had the newest BIOS version installed however when trying to install the newest version again it recognized the same BIOS was being installed and quit. When the BIOS back flash was enabled I was able to reinstall the newest BIOS version over the current BIOS which was the same version. It fixed my problem. I am assuming somehow updating the BIOS got corrupt. Hope this helps. Just a heads up BIOS updates could potentially render hardware useless.
