I started getting them too late in my drinking, and especially when I first quit. I still get them from time to time, but far less common and much less intense. For me it always starts with an odd feeling of impending doom, but with no source. My heart speed up and sometimes I feel weak and very shaky...like I'm going to have tremors or a seizure (but I never do ). And the just like that it's done.
I've told my doctor and they say it's just anxiety. I can't help but think all those years of drinking didn't burn out some brain cells and nerves that are partially responsible, but it's impossible to know for sure. I just keep reminding myself that nothing bad ever comes of them other than seriously freaking me out for a bit!