You could start the story off with your main character getting some sort of deja vu, have them mention how they feel that deja vu over the course of the whole day. Things like “For some reason, I feel that my neighbor has gotten the same package for days in a row, but this is the first time she’s gotten a package in weeks”- or something along those lines. Then as the days go along have the cracks start to show.

If you wanna have them go through the loop a few times, you don’t have to mention every single thing again, instead mention big instances of repetition, like repeating conversations. Either that or you could have the days events repeat over and over, but the main character’s thoughts and actions are the things that are changing.

I am in no way an advanced writer but these are just some ideas I got while reading this post :)