Superconductivity was recently discovered in rhombohedral trilayer graphene (RTG) in the absence of a moire potential. Intringuigly, superconductivity is observed proximate to a metallic state with reduced isospin symmetry, but it remains unknown whether this is a coincidence or a key ingredient for superconductivity. Using a Hartree-Fock analysis and constraints from experiments, we argue that the symmetry breaking is inter-valley coherent (IVC) in nature. We evaluate IVC fluctuations as a possible pairing glue, and find that they lead to unconventional superconductivity which is $p$-wave when fluctuations are strong. We further elucidate how the inter-valley Hunds coupling determines the spin-structure of the IVC ground state and breaks the degeneracy between spin-singlet and triplet superconductivity. Intriguingly, if the normal state is spin-unpolarized, we find that a ferromagnetic Hunds coupling favors spin-singlet superconductivity, in agreement with experiments. Instead, if the normal state is spin-polarized, then IVC fluctuations lead to spin-triplet pairing.
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