Random keystroke entry every 15 seconds

My surface laptop has started giving an issue whereby some letters or symbols (usually 2 or 3) will be entered into whichever program I am using. It will continue to do this until I reboot.

To be more specific, this morning it started entering 'ego' whilst I was working in One Note. It will then enter the same letters every 15 seconds into whatever program I switch to. EG, Excel, it will enter 'ego' into the cell I am in. If I do not move the cursor, it will keep appending so you get 'egoegoegoego' after a minute. If in a browser, it would enter 'ego' into the bar, in an email it would enter the letters or if it was happening now, it would just add to my typing.

If I move to a blank screen where it cannot input, then the system may ping.

Other things it has done include justifying One Note and Outlook emails to the right if I am working in them when it starts.

It may try to open some systems settings.

After a reboot, it might be good for a week or 30 minutes. When it restarts it will almost certainly use two or three other letters, 'fdm' was another yesterday.

I have contacted Microsoft and we reinstalled Windows (10 Pro).

I have been unable to associate any action or program to start it, an, trust me, I am trying!

I'm running Cortex XDR antivirus

any and all assistance appreciated.

SW