1992 Cadillac STS head lights

When I turned on my head lights in the past I had to bang the driver side light to get it to go on. Recently both light dont light till I give them a good fist bang to the headlight. This a.m. again the driver light didnt go on. Is this a headlight problem or an electrical problem such as a bad ground etc. If so how can I get a better connection. Headlights are original but expensive. I will replace if you thin that is the problem. Thank you Bigali