We live in a 6 unit 1917 coach house. Tonight a very quick and rather loud "fluttering" sound started in the middle of one of our living room walls. If I hit the wall it will stop for a few minutes, but then start up again. Could this be an electrical problem? I'm worried it might start a house fire.

Could be plumbing pipes, or duct work, or framing members settling. Could be electrical, but I doubt it. The only method to be sure will be to open the wall.

A rat had a seizure, What I think there maybe a loose wiring connection , that will buzz and when you hit the wall it makes a connection goes away but heats up again and comes back

It sounds like a critter to me. Unfortunately the only way to verify and be safe is to open the wall.