Reference: http://www.alfawzan.af.org.sa/node/14856
Question: I read [somewhere] that engaging in dhikr audibly after the obligatory prayer is a Sunnah; so what is the guiding rule regarding raising the voice [when doing so] since sometimes this causes inconvenience to those who are engaged in praying the Sunnah prayer?
Response: [Upon completing the obligatory prayer], you shouldn’t pray the Sunnah [prayer] until after [having engaged in] dhikr. Those who immediately stand to pray the Sunnah prayer as soon as the imaam completes the [obligatory] prayer are in error; this act of theirs is wrong. They should be patient and engage in dhikr [and upon completion, only] then stand to pray the Sunnah prayer. In addition, it is prohibited to pray continuously without a break in-between – either by speaking or moving [to another place to continue offering the prayer].