yes, it's probably the problem with hot plug settings of the iGPU. I ca reboot smoothly when I installed a new RX560 card and had all monitors connected to it, rather than any of the DP ports on the motherboard. If you don't have a graphic card, try to only use the VGA port and see if reboot works.
If reboot is ok, you may have to figure out how to fix hot plug configuration of your ports layout on the motherboard. I simply use two HDMI of my card, and poorly one VGA of the iGPU, without spending time on tuning framebuffers and hot plug settings.
Hope that helps you a bit.