I’m getting a weird dialog box pop up while using my iPad mini 5. It occasionally occurs when I’m in an app like Safari, Notes, etc. then set the iPad down on a table with it still on. The attached message pops up. This has been happening for a few weeks now, probably statrted after the last update.
I would wait for the next iOS 14.5 or iPADOS 14.5 due out sometime this month to see if it fixes your problems.
on my iPhone, shaking it brings up an undo prompt.
It sounds like it might be an accelerometer bug. On my iPad it tends to occur if I’ve typed in an app, even if I already closed the keyboard.

ETA: And I just posted this reply and set the iPad down and the message was then displayed. It isn’t that big of an issue, but it is annoying. The keyboard does seem to be more quirky here of late....