I would have to say that you have a loose heat shield on your exhaust. When in gear the rpm's are lower which causes more engine vibration. Also these vibrations can be amplified by a vacuum leak, engine misfire or worn motor mounts.
I had a similar option on my 2004 Honda Accord 4 cylinder in Ghana. It’s hard to get the fuse box in the aftermarket but fortunately, the problem was solved when I switched from the OEM halogen bulbs to led bulbs both low and high. Amazingly, the problem come back when I change to halogen and stops when I use led bulbs
It seems I am in the same boat as the OP. While I was vacuuming the car after the wife had been driving it for a few months the vacuum picked it up while I wasnt looking. So I found the diagram and pieced it out.
Honda Part No.:54716-T2A-A51ZA,
Lid NH587L (GLOSS ONE BLACK) is Ref No. 12 in the diagram below