Why did my iPhone beep and notification stating, “scanning your device”?

That's a scam and you should dump the free scrabble game you were playing. No one can scan your iPhone. NO ONE. But they'll try to scare you into believing you have something wrong you don't have. Get rid of that game as they are making off bad actors who try to scare you into buying services tools you don't need. And it's how the developer of that game makes money.

It’s part of a scam to scare you into falling for an ad they are going to show you.

The ad will claim you have viruses and try to scare you into downloading useless software.

This happened to my mom’s phone. She loves playing scrabble. She was complaining that her phone was beeping… I’m like force close the app… the beeping stop then came back again. Then over time it stopped totally. But that is crazy!