There is a great book by Katie Mack called The End of Everything. She runs through all the top theories like this. It's quite enjoyable.
One of the theories about the universe repeating has that ponderous nature that if this moment will be repeated forever any good thing you can do help someone will be repeated forever so if you have a choice to help or not you should think about that action being cemented forever. She doesn't go into free will and such, there are many other theories.
Yeah. When I read it, my life overall hasn't been that bad and my immediate thought was a sort of mystical comfort that the end isn't always an end. Then a few minutes later I thought, what if you had have been human trafficked or some other terrible nightmare. To repeat forever. If there is any truth to it we need to do all efforts to eliminate it today.
I'm not a physicist but I think the physics behind it is that they have observed some atoms instantly revert back to a previous state that they have been in. If it's possible that given a long enough time line one atom can go back at random any atom can and sort of like a random dice role. When infinity is in an equation anything that happens even in a 1-1billionth chance will happen because of infinity rerolls. That all atoms in the universe at random and at the same time revert back to a previous state they were in. The book doesn't like to comment too much on whether the theory is viable or not just that it exists.