Jackhammer like noise at low speed

There's a jackhammer like noise at low speed coming from the front end on Sunday. It is intermittent and once I get above 15 mph or so, it's gone. It didn't happen yesterday morning or this morning, but Sunday and yesterday afternoon it happened. It doesn't sound like brakes or suspension, so I'm assuming something in the motor or final drive or maybe the wheel bearings.

I have an appointment at the dealer but the Leaf tech isn't in until Monday. Any tips? It's a 2011 SL w/ around 30k miles.

Just some ideas which have happened to me with other vehicles: nail in tire (but it didn't leak) and failing u joint. All the wheel bearings that have ever failed on me howled, not knocked.

Curious to hear what they say.

It's definitely coming from directly under the hood right where the engine in an ICE car would be.

Can you record the sound & post it here?