Yes, this is static - I have it on my ES339 as well. It happens when I brush my hand against the pickguard, but also on the rear of the guitar behind the controls. I had a similar pickguard issue on my archtop that I solved by placing copper tape on the back of the guard and connecting it with a thin wire to the ground of the output jack. I'll have to do the same with the 339. The static from the rear of the guitar is an interesting problem. I can see that some of the wiring is laying on the wood of the back - not sure yet how I'll solve that.