It sounds like a faulty touch panel on the top of the speaker from your description - what happens if you switch off the touch controls in the Sonos App, when it’s back connected to your WiFi?

Thanks for your reply, I was trying to delete my question but can't seem to find a way to do it! It seemed to be interference caused by a nearby baby monitor. Moved the monitor and it's now working fine!! 

Ah that’s good news… it’s worth leaving the report here anyway, as it might assist others in the future who come across the same issue.