What year is your car?
I just took care of this problem on my 2003 EX I4. Just bought the car with 41,500 miles on it. Steering wheel shook badly at idle, stopped at lights, especially with A/C on.
There is a Honda Service Bulletin 04-024 that applies to 2003 and 2004 Accords. The dealer can check the rear engine mount, then if it is OK there is a new front mount and a "smoothing" kit that consists of some radiator bushings and a heavier plate inside the front lower bumper.
My car is out of warranty, so I bought the kit and mount for ~$210, installed it myself last night, and it is like night and day - very smooth now.
05 I4 Automatic, 43000 or so miles, the first and only owner - mine does this - a bit, usually when the car hasn't been running very long, when I'm in drive but stopped with my foot on the brake. I've heard it might be motor mounts, but the condition usually goes away once I've been driving for a while. Best as I can tell, this is just a Honda thing. Various friends of mine have owned Hondas over the years (civics mostly, a CRX, and one Accord) and all of them did this too (only the automatics of course). When I got my Honda I noticed it. Once in a while, I still notice it. I think it's just the vibration of the car being in gear and pulling against the brakes. RPM at start up is 1200-1500 for a few minutes, then once it drops to normal (7-800 RPM or so) and I'm stopped, it vibrates. It goes away, so I don't know if it is due to fluids not being warmed up or parts not being fully lubricated yet, but that's my guess.
I read something about the motor mount having two 'modes' and when stuck in the "firm" mode, vibrations have been noted. To fix, I believe the mount needs to be replaced. Mine seems to go away after a few minutes, so I'm not too worried at this point. You could take it in and see if a tech thinks the mount is bad.
The front motor mount has two chambers in it with liquid that flows from one to the other when you are stopped or idle so that you won't feel the engine vibration. There is a hose under the motor mount that connects to the intake manifold with a valve to turn on and off the flow of the liquid from the "hard" to the "soft" chamber.
Best thing to do is to check the valve itself that is sitting on the top and back of the intake manifold and check the hose for cracks. The valve kicks in under 1,000 rpm to "turn-on" the front active engine mount and shuts down below 1,000 rpm. A simple test is at idle to disconnect the vacum hose from the intake manifold and plug in the hole on the manifold itself with something so that the rpms won't go up and see if the idle is rough. If the idle is rough then the valve and engine mount is ok. If after you re-connect the hose, it is still rough then the engine mount and perhaps the valve has to be replaced.