There are so many reasons for the few second delay that I'd not fix this.
The cause could be the old HDMI handshake (can take seconds) to a driver you allowed W10 to install.
I turn driver updates in Windows off and I found them to break things that worked. Link follows.
Recently, when I login to windows. my second monitor remains black with cursor for a few seconds and after that it will start to display.
- I did not have this issue before.
- All my drivers are updated and there is not any issue with hardware (including gpu,....)
any suggestion what to do ?