The description makes me think it might be a Horseshoe Orbit [0], where something spends time in about the same circular orbit, but slowly bounces back and forth through the unoccupied portion.

Looking up 2025 PN7 [1], it says:

> Over time, it may transition between quasi-satellite and horseshoe orbits due to gravitational perturbations.

[0] https://en.wikipedia.org/wiki/Horseshoe_orbit

[1] https://en.wikipedia.org/wiki/2025_PN7

Would be neat to be able to get some photographs of it. Curious if it's a near-Earth asteroid or yet another case of a rocket's upper stage re-entering Earth orbit (like with 2020 SO and J002E3). An expected appearance of 1957 would be pretty early for the latter case (that's when the USSR launched Sputnik 1 and 2, and I'm pretty sure both those upper stages came back down a long time ago), but who knows?