Your dull grey Amalgams have a layer of tarnish from the silver and copper oxidizing. The shiney Amalgams have been polished down to bare metal, probably from chewing. Never polish Amalgams on purpose, even if your dentist offers to do so, because this will increase the amount of mercury coming off the amalgams.
Your amalgams are constantly releasing electricity but the intense shock you are experiencing is not likely from the microamps generated by your fillings. Might be a tooth nerve that is agitated from a cracked tooth or infection.
Can you describe the pain more? When does the shock occur? When you bite? When the teeth touch or when you apply biting pressure? Is it the same feeling you get when you bite on aluminum foil?