01 disco The steering locks up while driving, please advise

Yes, This I have found to be very dangerous. I went off roading last weekend and hit a large rock passenger side front. this caused a flat, so I purchased 4 new tires and had the disco re aligned. but ever since I hit that rock when I am drivinng the steering wheel will grab a bit in some spots but even worse while turning it will sometimes decide to freeze up or lock up and of course the vehicle is still in motion. can anyone advise to what maybe causing this issue, so I can drive safely and get back to fun in my rover

No doubt dangerous. My first impression was an ignition lock issue, but having hit a rick I would also check all steering linkage parts (suspension included such as the traction bar, sway bar, bushings, etc) and clearances to make sure nothing in getting caught, whether it be the tire, rim or other steering copmonents. You might elevate front end and see if there is any binding - just make sure that you elevate from axle to make sure the suspension does not drop down and give you extra clearance wher you may not have it. I would also check to make sure the PS fluid is full and that the serpentine belt is not slipping giving you a pause in the sterring to make it stiff. I have found the steering to be much more difficult than other PS steering when the pump is not working.

If you don't see anything I would take it to a good front end shop to inspect - locked sterring at high mph is not good, obviously.