Is the vibration in the form of your steering rim shaking up and down? As in vertical movements? And does it get worse during turns/cornering?
If so, it may be a bad bearing on 1 or both of your front wheels - if the bearing is badly worn the wheel can wobble on its axis (the hub). You can check this out by jacking the front of the car up, grab a hold of the front tyres with your hands and shake each of them hard (like as if you are grabbing hold of a person's shoulders and wringing the shite outta him). If the wheel that you are shaking (as aforesaid) wobbles, that wheel's bearing needs replacing.