Solved! Go to Solution.
OK, well, uninstalling YouTube appears to be an impossible task, however uninstalling the May update seems to have fixed the issue.
I'm not sure if it's relevant but I had YouTube Music installed but it had been automatically disabled as I never use it. I enabled it before uninstalling the update to YouTube so that might also have helped?
Well Well. There was a Bixby routine. I don't remember creating it but I've now disabled it. It wasn't specifically set up for YouTube, just any media but the phone is quite new and I don't think I've tried any other media app yet.
Thanks for this, it was driving me demented!
@Othafa: No problem. I'm not sure if this may have been activated via an in-app setting, as apps can change your system settings if the right permission is enabled, but I'm glad that I was able to steer you in the right direction.