Not uncommon, epsecially on Rangies and Discos for some reason.
You need to go through all the bits at the front end to check for wear / play. It's quite often a combination of things.
Steering Damper
Swivel Pins / Preloads
Wheel Bearings
Tracking
Tyre Balance
Steering Rod ends
Steering column Uj's
Some people will just throw a new steering damper on to make it stop, which is fine if that's all the problem was, but in many cases is just masking another issue.
If you have a workshop manual, it should tell you how to check all the above. If not, shout... they are all fairly simple procedures.