12 pro max boot up
Does your phone flash a logo apple briefly before the boot up apple logo shows up a few seconds later
iPhone 12 Pro Max, iOS 14
Yes, but it is not normal. It is an issue that encountered only iPhones shipped in January with iOS 14.3 pre-installed.
Here is the "main" thread about the issue you experienced:
https://discussions.apple.com/thread/252315567
As of today, we do not have an official answer from Apple, so we do not know if it is a software or a hardware problem (and at the moment there is no way to fix it).