Information about mechanics if possible!?

Hey guys looking for an answer to my problem! I have an 03 plate corsa 1.2 sxi and my car has started shaking really bad but it only seems to be when I take my car over a certain speed with a certain amount of revs and only when I have my foot on the accelerator!! I take my foot of the accelerator and the shaking stops no matter the speed or revs I put it back on and the shaking starts again!! Please can u guys give me some info on what this problem could be thanks