Whats you "job_queue_processes" init parameter value ?

And snp processes are just like other database daemons like PMON,SMON. So, you should be able to see if ora_snp is running.

If not (job_queue_processes is set to zero), change the value to at least 1. You don't need to bounce the database to do this. You can say "alter system set job_queue_processes=1" and the daemon will start.