Not recognising monitor if not already connected at boot

I have a monitor that I share between 2 computers, this means that sometimes when I boot my Manjaro PC, it is not connected to the monitor yet. I expect that when I change my monitor input to my Manjaro PC, that I would see the Manjaro login screen, but I don’t; I get a blank screen, in fact, my monitor doesn’t even think it is connected to anything. The only way I can fix this is to hard power down and reboot, now the monitor is connected.

I don’t know if it has any baring on things but I am running an Nvidia RTX3090 with proprietary drivers and the connection is DisplayPort.