It isn't the fuel pump or the flux capacitor...
I'm pretty certain it has happened with other cables, but I've been using the same one for awhile, so I'll try a different one. I sometimes use effects, but this happens regardless. I'll try cleaning the jack real good, too. I just replaced the battery...
I play through a variety of old Trace Elliot preamps, btw. (Love them!). I doubt it's that far down the signal chain, though. I guess I'm going to have to get absolutely forensic about this, but I was hoping this was something others would recognize right away and save me some time. I'll post whatever I'm able to determine...