If you play using a strap, loop the chord up between you and the guitar, then loop it back down and plug in the guitar. So that it is pintch and held in place by the strap. Often a wiggeling chord can make all kinds of static sounds. You can also check to make sure the little nut is tight where the chord plugs into the guitar. If that port is loose or dirty it will cause all kinds of problems. I have an old 1973 Hag that sometime in the 90's I took in to have the port replaced, the guy took a Q-tip and rubbing alcohol cleaned up the port and it was cured for a couple years then I had to do it again.

I really suggest the wrapping the chord trick.