Why is my iPad Pro randomly dimming and showing controls without input?

my ipad just went crazy -- started spontaneously dimming the screen and showing the control items, like volume and screen brightness. Nothing was being touched on the touchscreen or the attached keyboard when all this started. I finally did a hard power-off because the touchscreen wasn't responding. [11" ipad pro (M4) running iPadOS 18.5.]. Any ideas as to cause? Cause for concern?

[Re-Titled by Moderator]