The c-axis resistivity rho(c)(H, T) of stage-4 MoCl5 GIC between 1.9 and 50 K has been measured with and without an external magnetic field along the c axis (0 less than or equal to H less than or equal to 44 kOe). The interior G layers form a bottleneck to the c-axis conduction. The T and H dependence of rho(c) is mainly determined from that of the bottleneck resistivity proportional to the in-plane resistivity of interior graphite layers. A logarithmic behavior of rho(c) in the form of In(T) and In(H) indicates that the two-dimensional weak localization occurs in the interior graphite layers. The T and H dependence of the in-plane conductivity derived from rho(c) is discussed in terms of scaling relation predicted from the theory of two-dimensional weak localization.