This ion is not flipping. Its true electrons sit in both places at once.
Chemists draw three Lewis structures, moving only electrons, never atoms, with double-headed arrows.
The real ion is their blend: every C–O bond identical, about one and a third.
Delocalized electrons spread the negative charge over more atoms, so no single atom is overloaded.
So the hybrid is lower in energy than any single structure: resonance stabilizes the molecule.