Alright I'm having this problem with my guitar string and I think it has something to do with resonance .
When I struck a string (Especially high E , B and G) one or two other strings start to vibrate by their own and of course the pickups took all that result in a very unwanted noise in background.
Is this has something to do with my recent new strings set? I stringed the guitar with Elixir Nanoweb Light gauss with exceptional of Low E string from my old strings (I think it's 0.50 or something... Elixir Light has 0.46 low E)
It might be ur bridge. If something in that is loose, then its gonna vibrate like crazy, especially in a hardtail/trem bridge. I think a saddle might be loose. What kind of guitar do u have??