Hour in red

So, I changed my phone to an IPhone X a few weeks ago and yesterday I started to see that in the bar where the hour appears it was in red (like when you are recording the screen). I didn’t record anything and when I tapped on it, it stopped and I try to find any recording but there wasn’t any.

And today, when I took a photo on instagram it showed again to then disappear. I don’t know if it’s common to do that.