2005 Honda Odyssey Vibration at various speeds

There is a vibration at various speeds while engine is in process of gaining speed. It happens between 30-40 mph, 45-50 mph, and 60-65 mph. If speed increases to 70 mph or above, it seems to subside. Especially when in the 30-40 mph range, the vibration seems to be the strongest and when it starts, I can take my foot off the accelerator and then push it harder to get past the vibration.

Both of my brothers' wives also drive an Odyssey and have the same problem.