Why does powerpoint go to different page when I don't touch my mac? On my Mac (specs below) MS Powerpoint (specs below) behaves very strange:
It goes to a different page (page-up or page-down) on its own.

Even when my Mac is not connected to power source (so no static electricity), and even when I do not touch the computer in any way.
And there are no bluetooth mice or other devices connected.

It does this in edit mode, and annoyingly also in presentation mode.

I have no idea if this is a powerpoint or a Mac issue. This strange behavior  happens only in powerpoint. It does not happen in keynote, or other MS Office apps. I have no idea even where to look for possible causes of this problem, let alone solutions.

EDIT: Additional info after useful comments:


Behavior happens in edit mode as well as presentation mode. 
Happens in different presentations (created in powerpoint on Mac).
The presentations have no transitions, animations or timings.
Behavior happens sometimes, so it is hard to check. I can go for days without problems, then all of a sudden (this afternoon) in the middle of presenting for a group, powerpoint becomes recalcitrant and randomly does autonomous  page-up or page-down in the middle of my story. And a couple of hours later, no problem (different wifi-network, maybe that has something to do with it..)


What could be the cause? Where to look for source of problems or solutions to this strange (but very annoying) issue?

PS: Mac = MB Pro 2017 - without touchbar - running 10.14 Mojave (but issue was already happening in High Sierra)
Powerpoint = MS Powerpoint for Mac version 16.17 (180909)
At the school where I work, those who have the oddest problems sometimes can't remember when they last restarted their MacBooks; have many apps open perpetually with some apps having many documents open within, etc. Purists scoff at the need to restart macOS, but I think it is the first, best step to resolving odd behavior.

In addition, if you do use a BT device at your desk, (or where you do most of your work,) and leave it behind, disable BT when you are presenting elsewhere.