White screen appears on booting Mac and desktop doesn’t appear for so long. To resolve this issue, just safe reboot your Mac with safe boot.
When booting begins and the moment you hear the sound of booting in your Mac, hold shift key and it will start the computer in safe boot mode.
This issue generally happens when your computer running with lack of free space. So, try deleting unnecessary data and free space in some GBs in safe boot mode. Once done, restart the Mac normally and it will be okay now 🙂