povremen

1. occasional; periodic
   Sutra se očekuju povremene kiše. — Occasional showers are expected tomorrow.
   Imam samo povremene bolove u leđima. — I only get occasional back pain.
2. (of work) occasional; casual; intermittent
   Tokom studija je radio povremene poslove. — During his studies he did casual jobs.

The adverb povremeno "from time to time" is very common. Do not confuse with privremen "temporary" (limited in duration): povremen posao is work done now and then, privremen posao is work for a limited period.