I have a 1998 Acura 3.5 RL

The engine is absolutely quite - when on neutral. i even tried putting
car on neutral & with brakes pressed increased the RPM till 3000 - and
there was no vibration.

When the car accelerates from 0 to 30/40 .. the gas pedal feels little
stiff .. and hear a wierd humming sound.

When i stop at a traffic light - the car vibrates a bit.

do you think the problem is with the transmission system? should I
consider like a transmission flush, etc?

any other potential suspects?

would appreciate your response