  We investigate the mesoscopic disorder induced rms conductance variance
$\delta G$ in a few layer graphene nanoribbon (FGNR) contacted by two
superconducting (S) Ti/Al contacts. By sweeping the back-gate voltage, we
observe pronounced conductance fluctuations superimposed on a linear background
of the two terminal conductance G. The linear gate-voltage induced response can
be modeled by a set of inter-layer and intra-layer capacitances. $\delta G$
depends on temperature T and source-drain voltage $V_{sd}$. $\delta G$
increases with decreasing T and $|V_{sd}|$. When lowering $|V_{sd}|$, a
pronounced cross-over at a voltage corresponding to the superconducting energy
gap $\Delta$ is observed. For $|V_{sd}|\ltequiv \Delta$ the fluctuations are
markedly enhanced. Expressed in the conductance variance $G_{GS}$ of one
graphene-superconducutor (G-S) interface, values of 0.58 e^2/h are obtained at
the base temperature of 230 mK. The conductance variance in the sub-gap region
are larger by up to a factor of 1.4-1.8 compared to the normal state. The
observed strong enhancement is due to phase coherent charge transfer caused by
Andreev reflection at the nanoribbon-superconductor interface.
