cron job from boot/reboot and every 10min after

Question

despite reading many things on cron I am not able to achieve what I am looking for :

• run a monitoring script every 10 minutes from the server start/reboot time.

I was able to make it work at 10min after a reboot/start with :

@reboot sleep 600 && bash ./monitoring.sh | wall

however I did not have the repetition after. the other way I was able to do it was :

* * * * * sleep 600 && bash ./monitoring.sh | wall

but this would wait ten minutes and broadcast each minutes after.

if I change to :

*/10 * * * * sleep 600 && bash ./monitoring.sh | wall

it does wait 10 minutes after start/reboot, but then broadcast at each 40, 50 minutes.

Can it be done with cron or do I need to go the script way ?

thanks.