This seems to be caused by the flush handle sticking. I can give the handle a gentle upward lift, the outer edge of the handle rises maybe a quarter inch, and then in a few minutes, the ripples in the bowl cease.
The toilet gets used by my kids, and none of them seem to have the "lift the handle" edict figured out.
So what do I do now (dumb question, I admit it)? The flapper valve is in good shape, there's no buildup on either the valve or where it seats, the chain is long enough but not too long and doesn't tangle on itself. I just need to figure the "trick" to make the handle stop sticking.