Very intermittent pain in middle of 1st metatarsal

For the past few months, I've been having very intermittent sharp pain near the middle of my left 1st metatarsal (it feels like it's on the side of the bone.) The pain is not dependent on load; sometimes it happens while I'm sitting, sometimes while I'm walking. When it feels fine, I can jump up and down, do yoga, walk, whatever, with no issues. It usually goes away after a few minutes, but it is annoying.

Other than having flat feet (as in, the wet-foot test leaves no indication of an arch) no issues with my feet. No swelling, redness, inflammation, or tenderness. When it's acting up, applying pressure to the painful spot does not change the symptoms. If I'm sitting, standing on it makes it neither worse nor better, and if I'm standing, sitting doesn't help. The only thing that makes the symptoms go away is time. (Usually three or four minutes.)

I'd just ignore it, but it seems to be happening more frequently... At this point, it isn't often enough to restrict my activity in any way; it's just annoying.

SirWired