The dynamics of a thin layer of atoms between two rigid substrates is studied by molecular dynamics. Simulations exhibit different regimes. For a low relative velocity of the substrates a stick-slip regime concerning alternating atomic channels, which is reminiscent of intermittency in chaotic systems, is observed. At a high velocity the system reaches a sliding regime, for which the simulation results can be described by an effective intrinsic friction due to an energy exchange between the moving top substrate and the atomic film.