If you're using a somewhat modern shell there is $RANDOM which gives you a 15 bit random number. So e.g. sleep $((RANDOM / 546)) but I guess most cron job

If you're using a somewhat modern shell there is $RANDOM which gives you a 15 bit random number. So e.g. sleep $((RANDOM / 546)) but I guess most cron jobs run with an extremely conservative shell that might not have it.