John Gill Commentary Job 32:5

"And when Elihu saw that there was no answer in the mouth of these three men, his wrath was kindled." — Job 32:5 (ASV)

When Elihu saw that [there was] no answer in the mouth of
[these] three men
That could be called an answer; nay, when he perceived they were quite nonplussed and silenced, though men of years and experience, and reputed wise and knowing:

then his wrath was kindled ;
his spirit was stirred up; his heart was hot within him; he burned with anger against those men; he was all on fire, as it were, and wanted to vent his resentment.