Many cron systems have this functionality. At least anacron and cronie (RHEL) supports the RANDOM_DELAY variable. Check your man 5 crontab. There's also system

Many cron systems have this functionality. At least anacron and cronie (RHEL) supports the RANDOM_DELAY variable. Check your man 5 crontab. There's also systemd timers which can replace cron jobs with RandomizedDelay. Before that, people used to include a random sleep in the actual job. Personally, I tend to not use these things and instead pick a random start time when provisioning the job. That way the time delta between run is constant, which is often desired.