Some users experience a long black screen before the logo/menu for Dawntrail on their first-time execution of the game. FFXIV is trying to compile shaders so it is best to leave it. 

But having said that, be sure to update your Nvidia driver: https://www.nvidia.com/en-us/software/nvidia-app/

Or use DDU to uninstall your driver prior: https://www.guru3d.com/download/display-driver-uninstaller-download/

The shader compilation is an intensive process, so some system may throttle under this load. Laptops may take up to 10mins for this process.