The adverb 不时 "from time to time"
The adverb 不时 indicates how regularly an action is done.
The adverb 不时 
indicates that an action is done occasionally or irregularly. It is followed by a predicate expressed either by a verb or a verb phrase.
不时 is often followed by the particle 地 .
indicates that an action is done occasionally or irregularly. It is followed by a predicate expressed either by a verb or a verb phrase.
不时 is often followed by the particle 地 . Pay attention
不时 is used in written language.
Examples
远方不时地传来鸟叫声
From time to time, birds chirp not far from here
yuǎnfāng bùshí de chuán lái niǎo jiào shēng
要抬起头，不时看看四周
Lift your head up and look around from time to time
yào táiqǐ tóu, bùshí kànkan sì zhōu
他还是感到伤口不时疼痛
The wound still hurts him from time to time
tā háishì gǎndào shāngkǒu bùshí téngtòng