Front end shimmy

I have a 2006 jimmy & when driving on paved roads at 60-70 kmh front wheels shimmy & shake so bad 
any idea why , I only have 50,000 km on it 
 

It's more than likely one or both of the king pin bearings on the front axle, they are notoriously good at failing. You will probably als have oil seaping from the steering balls on the ends of the axle. Fear not, the parts are readily available in the shop in the top banner and in the information section there's a comprehensive how to guide.

Out of balance wheels is the primary cause, wear in the king pin bearings or any of the joints in the steering linkage will exacerbate the situation.

No wrong answers here, so I'll just add my 2 cents.

Start cheap and free.
1) Jack each front wheel off the floor and whilst holding at 12 and 6 o'clock feel for play or movement by pushing pulling. If you feel nothing I would remove the brake caliper (it's simple to do), refit the wheel and try again. Sometimes the brake caliper can prevent movement unless you are very strong. If you feel nothing, and you don't have the oil leak indicated by Lambert, it's not likely to be the Kingpin bearings. Not likely, but not impossible.
2) Whilst you have the wheels in the air check your ball joints and bushes for any movement or play, repair if required.
3) If you have done all this it's time to get your wheel balance checked, time to spend a little cash.
4) If it's still happening it's time to visually check your kingpin bearings. It's possible they are a pile of rust, but a kit of parts (£50 each side) and a few hours and the jobs done.
5) If it still wobbles fit a steering damper and hope it sorts it or carry on trying to locate, 1 to 4 are the must do first group.
Good luck.
Mike