Not sure what to suggest offhand, but answers to the following questions may be useful in focusing our thinking. I will say at this point, though, that what you are describing sounds to me like it goes beyond normal static effects. My guess is that something is wrong somewhere, in the system or in the ac power distribution.
-- Are the connections between components balanced or unbalanced?
-- Are the ac power plugs of all of the components 3-prong, and is the third prong (the safety ground connection) defeated on any of them via a cheater plug?
-- Are the ac power plugs of all of the components sharing a common ac outlet, via a power strip or power conditioner, or are any of them plugged into separate outlets or separate dedicated ac lines?
-- If you are using a power conditioner, does it separately filter the ac to the preamp and power amp? And what model is it?
-- Is there any likelihood that interconnect cables may have been damaged around the time this started happening, such as by being stepped on?
-- How old are the components?
-- Does the system have protection against electrical surges?
-- Do you feel a mild (or not so mild) static discharge shock when this happens?
-- Do you feel a shock if you touch a component while everything is turned off?
-- Does it happen with line-level sources, phono-level sources, or both?
-- Does the system include a phono stage, either within the preamp or separately?
-- Do you have confidence in the integrity of the house's ac wiring? For instance, is it conceivable that there could be a missing ground wire or open connection somewhere?
Regards,
-- Al