Odd electrical issue

[trilobite]

So yesterday I go to the parking lot and hop in my car and turn the key and nothing happens. Nothing at all. I notice I have no power.

I open the frunk and take the battery cover off just to see if there is anything worth noting, which there wasn't. I closed the hood, and as soon as it dropped closed, the car started chiming and the radio came on. So I hopped back in, turned the key, and instead of starting, all the power shut off again.

I once more opened the hood to make sure there wasn't a loose connection to the terminals. (There was not.) I closed the hood again. As soon as the hood dropped shut, everything came back on. Once more, I jumped in and turned the key. Nothing.

I once more opened the battery compartment, and out of frustration, I smacked the top of the battery with my hand pretty solidly and everything turned back on. I got in, it started right up and I have had no issues since yesterday afternoon.

Is this likely to be a harness issue, or did I simply need to reassert my dominance?