Temperature dependent positron lifetime measurements have been carried out in n-p-ethoxybenzylidene-p-butylaniline. The samples were prepared either by quenching or slow cooling from the liquid crystalline phase of the compound. The lifetime measurements were performed in the heating cycle of these samples in the temperature range 165 K to 355 K. The behaviour of the quenched sample is found to be quite different from that of the slow-cooled sample. The temperature dependence of o-Ps pick-off lifetime in the quenched sample, unlike the slow-cooled sample, exhibits eight distinct peaks at various characteristic temperatures before the material undergoes a glass transition. These peaks have been attributed to various intra- and inter-molecular modes executed by the molecules. The characteristic frequencies of some of the modes observed in the present work agree well with the literature reported values obtained from FIR and Raman studies, for others no such information is available. The present study demonstrates the usefulness of positron lifetime spectroscopy for investigating molecular motions.