Ted here from Shopify, thanks for reaching out to us. :-)
Are you still on a trial, or have you chosen a plan and the trial has not finished? If you are still on a trial and have not selected a plan, I would not recommend selecting a plan just yet. This way, when you are ready to come back to Shopify after 10 days, our Support can review your account and possibly add a trial extension to your plan. This can only be applied once to an account, but please make sure to reach out to our Customer Support via this link and we'll take a closer look. If you had 5 days left on your trial previously, just let us know and we will take this into account as well.
If you have selected a plan, we wouldn't be able to add a trial extension to the account. You would have the option of closing the store and then re-opening it later when you are ready, or you can pause your store for $14 a month. Pausing a store will still grant you access to your store's admin and the only thing that can't be used is the payment gateway. You should be able to pause or close your store as mentioned here.
How are you finding Shopify so far? Do you have an idea of the type of store you would like to create or the products you would like to sell?
If there is anything else I can help you with, please let me know, I'm happy to help!
Thanks a mill,