Black dots shuffling across iPhone screen after reboot

So within the matter of five seconds when I rebooted my phone, I have all of these black dots. They’re just not sitting on the side. They are moving all over my screen so now I’m trying to figure out what the **** just happened to my phone. does anybody know because my name just sitting on the sides mine are floating all over my screen. I will never buy another Apple phone in my life. I am going on my third 15+ an apple will not do nothing about it never ever again. I’ve never stepped foot in Apple Store until I upgraded till this 15+ never will I get another iPhone all of a sudden you have these black dots what are they and what do they mean? Apple has gone down to the bottom of the list.

[Re-Titled by Moderator]

Original Title: I have the black dots that everyone’s talking about but mine are shuffling all over the front of my screen. What is it?