How to Send email reminder to Assignee every Sunday if Item status In-progress or not started.

@Md_Tahir 

Good question here and there are two approaches.

1. You can use a task based reminder that runs on each item, so the reminders would consistently go out say every 7 days, but the date would vary based on when the item was created, submitted etc. 
2. You can use a site workflow and schedule the workflow to run once a week on sunday. It could query the list to see what all items don't have a specific status and then email a reminder for those. The key with this one which is doable, would be to ensure that the user has a way to update the item so it doesn't show up on the list anymore if acted upon. 

Option 1 is more standard and it drives a direct business process such as "reminders will be sent every 3 days until the task is completed". Every Sunday is a bit more tricky because you have to account for calculating Sunday but its doable.

I don't have time right now to build it out with screenshots, but this should get you started.

I just posted a reply to someone with a very similar workflow layout:

Send Email Notification of New Added Changed Items Once Every Month

Create a site workflow that queries the list. 

Filter the query based on your status criteria. (If you need to filter on task start date too, do that here.)

I suggest only pulling the ID at this point if you need to query multiple fields from the item, which it sounds like you will. Make sure to use a collection variable.

Loop through the ID variable and use that to re-query the list filtered on the ID.

In the second query, pull each field you need into single line of text variable (or whatever data type you need).

For your instance, you'll want to send the email notification inside the loop, because there will be multiple emails going out. One for each record returned.

You shouldn't need the Build String action, because you'll simply build it inside the Send Notification action.

Hopefully that gets you started.