No worries. It can be disconcerting at first but you get used to it.
Not like cars of old where the braking servo assist would die as soon as the engine stopped.
If you have hill assist this is a nice feature. When you have pulled up and engine stopped you can take your foot off the brake and wait. When ready to pull away dap throttle and engine will start, press further and hill hold will release and you are away.
Another surprise you may not have had yet is when you have pulled up and engine has stopped - you have not got out of car yet and are chatting through the window. All of a sudden car decides enough is enough and starts engine again.
These forums are a font of knowledge and why I am here too. Enjoy the car.