Were you driving in 2 wheel drive or 4 wheel drive when it locks up? Sounds like axle wind up (in 4 wheel drive). This is quite possible, especially if you're driving on hard pavement.
I've never experienced it on my tractor (but other then a little work on the road when plowing snow, this machine never sees hard pavement).
I suggest you ensure you were in 2 wheel drive (maybe the selector lever was in the wrong position). If this happens again, and you have a front end loader, stop the tractor, lift the front end (so the front wheels are off the pavement) then lower it and see if that corrects the "lock up". If it does, I think your tractor's 4 wheel drive is engaged or engaging during the transport.
Kenny's thoughts about bad bearings is possible too, but I would think that would show up during any movement, but dnj12345 writes this never happens while operating in his yard (off road).