It could be static. Just to respond to a few things you talked about:
I got shocked through both the yoke and the throttle. Usually it was through the throttle, but sometimes I felt the shock through both yoke and throttle.
The yoke is painted but the paint is a little worn where I usually hold it.
The airplane has static wicks. At least three on each aileron. I think there are a few on the elevator as well.
When I got zapped, it was about 65F and the dew point was about 63F. Was worried about fog forming but it didn't happen. Very humid. I got shocked lightly once or twice during run-up. Then I really got shocked a few times after I was airborne. I also got zapped shortly after landing roll-out. But not during taxi after.
The club mechanic happened to be on-duty so I discussed this with him. An instructor and I flew the plane shortly after (same night) to see if we could replicate and isolate the problem. Neither of us got shocked.