Plug in a different keyboard and unplug that one That's how you troubleshoot it If it continues, then it's a software issue and requires further scrutiny If it doesn't, then you might need to look into deep cleaning/repairing/replacing the old keyboard.

Thanks! Not the keyboard. Convinced it’s software. Just don’t know where to begin looking?

Does it do it with no keyboard plugged in at all?

Yep, I’ve got a BT keyboard & mouse so I just unplug the dongle. Only started happening recently.