faltering
n.staggering or losing your balance while walking. It can also describe a voice that is shaking or a plan that is starting to fail.
n.staggering or losing one's balance while walking; failing to maintain a steady course or a steady voice. Often used to describe a physical stumble or a weakening of resolve.
“The old man took a faltering step toward the door.”
“After the long hike, her legs felt weak and she took a faltering step onto the uneven rocks.”
“The speaker's faltering voice betrayed his nervousness, though he managed to finish the speech with a final, steady breath.”
“Reviewers are struggling to keep up, and the system appears to be faltering.”
From falter + -ing.
Etymology adapted from Wiktionary, available under CC BY-SA 4.0.