Anders from the Social Care Team here. Thanks for reaching out today!
To start up a Shopify store, a business license is not actually required. However, your payment provider (ie. the means your store is able to process payment online) may require you to have a business license. You can find a list of supported payment providers in Romania HERE.
Depending on your local law, it's possible that you may also require a business license once your store begins to make sales. I suggest checking with your local authorities to be sure!
If you have further questions, feel free to follow back up!