@mancsgirl: If the problem persists following the steps provided by @BandOfBrothers, I also recommend heading to Settings > Software update > Download and install, followed by Settings > Security and privacy > Updates > Security update, to ensure that your phone is fully up to date. Furthermore, open the Galaxy Store > Tap the 3 lines in the bottom right > Updates, and install any available updates for the Camera app.
To check for any potential hardware issues, please head to the Samsung Members app > Support > Phone diagnostics > Camera, and follow the on-screen prompts. If you see an 'Action required' notification in the summary at the end of the test, then please reach out to our Support Team via the link below, and an advisor can arrange for the phone to be inspected by an authorised Samsung engineer.
https://www.samsung.com/uk/support/contact/
Alternatively, you can arrange the inspection yourself on our website by following the link below, or via the Samsung Members app > Support > Repair service > Request service.
