Hesitation, when speaking a foreign language, is studied through its components: beginnings, pauses, and repetitions. This paper aims to identify, through the study of this phenomenon, vulnerable zones among Iranian learners when they speak French. A case study of 30 adult learners shows that hesitation is not random and at different levels (A1 to B2) it is differentiated and divided into fluent, semi-fluent, and disfluent utterances. Problematic linguistic elements and those structures that have not yet been internalized make up speaking vulnerable zones, cognitively manifested by hesitations. The results show the least fluent learners at each level had more finished beginnings. The less a learner was fluent, the more they had in-word beginnings. In addition, the number of modified beginnings was greater than the finished ones when more fluent learners spoke. There are, therefore, implications for oral proficiency assessors who may conclude that the learner knows the rules but still has to practice to reach fluency. The results also show that there were more filled pauses than silent ones at all levels except A2. At B2 level, there were considerably less pauses, a sign of learner autonomy.