Is it a cinder block/concrete wall, or a railroad tie wall? Either way, your footer has either failed, or wasn't built properly in the first place.
Some rebar driven into the ground to support the wall can prevent a collapse in the short term, but I imagine you'll need to replace the entire wall before too much longer. A couple more freeze/thaw cycles and your wall isn't going to be much of a wall.

I can't help on the recommendations, other than you could rent a bobcat and do it yourself if you were so inclined. Not a technically difficult job, but pretty labor intensive.