Thanks. I'm well within warranty and couldn't sort before I went on holiday. I've since given the phone a proper clean including gently ridding the port of dust etc. Strangely - one cable worked fine and now more cables seem to work - particularly in a travel GaN charger I bought for India.I've also had the same issue with the last few top end Samsungs I've had.
However I think its possibly down to some cables? It tends to start if I plug it into a 'non' samsung cable - started mostly on my S23 after I plugged it into my mac usb charger...
When it happened on my S22U Samsung came out and replaced the port for free - but still annoying.