Molecular dynamics in a model bilayer compound C6H13NH3Cl is Studied by H-1 spin-lattice relaxation in the laboratory and in the dipolar system as; well as by N-14 nuclear quadrupole resonance. In the low temperature monoclinic phase, the NMR data show the presence of a slow motion which is presumably the 120 degrees reorientation of a C-NH3 group around the C-N bond. In the high temperature tetragonal phase, the nuclear magnetic and quadrupole resonance data show the presence of two motions in addition to the reorientation of the C-NH3 groups: a fast motion causing a strong temperature variation of the N-14 NQR frequencies, and a slow motion dominating the proton spin-lattice relaxation in low external magnetic field and in the dipolar system. Various models of molecular dynamics in the high temperature tetragonal phase are examined in relation to the experimental data.