I'm a developer with Cognito Forms.
If you have Save and Resume enabled on your form they will be able to get an email when they first save their form. We do not have a system in place to resend the link at a later time.
You can also set up and send out a Share Link from the Entries page. This system is not automated so you will have to go in and manually generate this for the user. This will let you provide them with an edit link to pick up editing/filling out their form where they left off.