Hello Sarah,
If it were mine, I would be searching out a trusted localish independent, and seeking advice and inspection there. Ideally, you need to find somewhere where you can talk with the actual mechanics, rather than a receptionist.
Kind regards,
Gareth.
My 2014 did something similar when I got it. The start stop often had the deactivated symbol on the dash and on the occasion it did work it didn’t restart the car and would beep and put error lights on the dash. Turning the ignition off and back on would restart it but slowly. That was caused by a faulty battery. Replaced and it’s been fine since.