Many cron jobs run at 0 minute of the hour. Especially during midnight, multiple scripts might be running concurrently, causing spike in server load. It is a good idea to use different minutes if the task is not time sensitive. I came across this interesting way of introducing random minute execution in cron.
0 0,12 * * * python -c 'import random; import time; time.sleep(random.random() * 3600)' && certbot renew