Starting from Pega7.3 you have Agent management landing page which has checkbox instead of radio buttons which can be used to select multiple agents and start them or stop them at a time. So if you are on Pega7.3 or above version you can navigate to Designer Studio>System>Operation>Agent Management.
If you are using Pega version below 7.3 then SMA is the only OOTB option to enable and disable agents before and after restart of JVM.
Why do you want to stop the agent before JVM restart and start the agent afterwards?
In Pega 7.1.7 or 7.1.8(not sure the exact version) there are issues in which whenever there is a Database connection failure few agents goes into hung state. So may be to avoid this issue you might have been instructed to perform this task when Database is going offline.