Timer boundry event problem

In my BPMN, i have automatic validations to do through boundry timer on user task.
The boundry timer is set with cycle and cron value ‘0 0 2 * * ?’, i have about 30 000 declenched by night.
Sometimes the engine don’t response until restart it, so jobs are a cumulated and restarted as soon the engin is restarted, the problem when the 30 000 jobs started, the users can’t work on application it so slow.
I want know if there is any setting to do, to skip execution of jobs in the morning (so skip actual due date if we are on point time 6h-20h)