Why is my electric guitar making a buzzing sound?

I have a Cortez Les Paul style electric guitar. My uncle gave it to me. I believe he said he bought it in 1979. He rewired it before giving it to me. However, I have been noticing a loud, incessant buzzing coming from my guitar whenever it's plugged into an amp and the rhythm pickup is turned on. The buzzing stops whenever I touch some of the metal on the switch or the jack or a pickup with my finger. I know next to nothing about the inner workings of an electric guitar, so this problem is beyond my ability to fix. I would appreciate any help you could give me.