1987 Chevy Camaro

Does the engine make any ticking noises at that time, and is the oil pressure good until it warms up? It could be too light an oil, or may be in need of an oil change. Before getting too worried, put a manual oil pressure guage on it just to be sure.
Sometimes a bad sending unit will give you a false reading, a manual guage will not. Hope this info helps.
Mickey-d