Delays in receiving Messages on iPhone 15.6.1

I only receive Messages (i.e. iCloud Messages) on my iPhone when I unlock the phone and begin using it.

At that point, the messages start coming in quickly (or at least I start getting notified about them quickly).

Few things to note:

a) this started in the last three months or so?

b) I do receive iCloud Messages in real time on my Mac so it's not like it's getting cached/stored/stuck somewhere

c) I don't see anything in Notifications settings that's jacked up

I've done the standards (reboot, reset, quit all apps, etc.)

Thanks, Regards, Rick