This is the 4707th most frequent Japanese word.
時折
"時折" means "occasionally" or "from time to time" in English.
In this sentence, '時折' is used as an adverb to indicate that the action happens from time to time or occasionally.
時折雨が降ることがあります。
It occasionally rains.
Here, '時折' shows the intermittent nature of stopping during an activity.
時折立ち止まって風景を眺めるのが好きです。
I like occasionally stopping to enjoy the scenery.
In this usage, '時折' implies that questions arose sporadically during the lecture.