I'm not technical enough to know electrostatic from non, but my 10" Admiral bakelite set with original CRT does this same thing. The flickers seem to be in random "corners" of the screen but mostly the bottom right, they vary in brightness and there can be a few to several seconds between them. The set has to have run for a while before it will do this after shutting down. If I turn it off after only 5 or 10 minutes I will get a white dot but no flickering.

Growing up the sets I watched as a kid did more of the shriking to a dot routine and I don't remember any flickering like my Admiral makes.

With my rudimentary knowledge I was figuring it was a situation of left-over electrons like Charles describes above. Glad to read here that this doesn't appear to be a sign of any pending trouble.