Me and my family have the same problem since today.
we are using iPhone 14 Pro, iPhone 13 Pro and iPhone 11 Pro
Almost all apple apps are troubling, and some more as well. I cannot open phone app, message app, contacts app anymore, I only got a white screen and then the app crashes. I cannot phone or message anymore. The Find my app has same issues, sometimes it freezes, sometime all my AirTags vanished, then appear again. Also apps like Amazon or Facebook messenger keeps freezing at start, my Apple Music is able to find music, but I can't play any song. I tried two restart methods, volume up/down, then power and slide the control to shut down. And keep holding the power button to force a restart. Nothing worked for me. My iPhone seems dead since 6 hours.
I got a MacBook Pro M3 Pro and an iPad Pro, and all these devices are running fine. My wife's iPad Air is also working. Only our 3 iPhones are dead.
Does messages/contacts/phone app use iCloud at startup? It seems that the phones have trouble with iCloud. But I can access my iCloud files. Also photo sync was not working for a while, at least this started again. I don't want to logoff from iCloud because I don't know if I will loose some data. Why this happens to my entire family?
Any ideas how to handle this? I'll wait for tomorrow and check if the issue still present.