Does anyone know how to add a light box pop up on a timer, on Shopify? I want customers that go to my website and see a welcome post in a light box that covers the whole page and then automatically closes after about 3 sec. then it closes and you can see my website.
Sorry you are facing this issue, it would be my pleasure to help you.
Welcome to the Shopify community! 
Thanks for your good question.
Please share your site URL,
I will check out the issue and provide you a solution here.