For movement:
* Stumble: To move unsteadily, as if about to fall.
* Stagger: To walk or move unsteadily, as if about to fall.
* Teeter: To move unsteadily from side to side, as if about to fall.
* Sway: To move back and forth gently.
* Pitch: To move forward or backward suddenly and sharply.
* Careen: To move or swerve in a dangerous way, especially out of control.
* Totter: To walk or move unsteadily, as if about to fall.
* Flounder: To move clumsily or with difficulty.
* Wobble: To move unsteadily from side to side.
* Jerk: To move suddenly and abruptly.
For sudden change:
* Plummet: To fall suddenly and rapidly.
* Plunge: To fall or dive suddenly and rapidly.
* Dip: To suddenly move downward.
* Spurt: To suddenly increase in speed or activity.
* Surge: To move suddenly and powerfully forward.
For sudden change in feeling or condition:
* Slip: To suddenly lose control or stability.
* Slide: To move smoothly and gradually downward.
* Dive: To suddenly and rapidly move downward.
* Collapse: To suddenly fall or give way.
The best word to use will depend on the specific context of the sentence.