Phone is Starting screen is displayed during boot on Galaxy device
Devices with Android 9 or higher will automatically enable file-based encryption if it has a PIN, pattern, or password set up. During the boot process, the phone will display "Phone is starting..." and the screen may be blank for a few seconds while encryption is taking place.
As *FBE (File Based Encryption) activated during booting has being newly applied on your Galaxy device, you may feel that your device takes more times to complete system booting than other devices.
*FBE is one of Google security solutions.
Thank you for your feedback!