I don't think it's not require restart the SAP until if you are having any changes the instance profile, for refer check this link https://blogs.sap.com/2013/09/26/step-by-step-setting-up-operation-mode-for-beginers/
From your Question Thread, its not clear if you are looking for SAP Application Operation Modes switch or its related to your OS or some other tool.
If its related to your SAP Application operation-modes, then Change in Operation mode does not require SAP application restart. Operation modes can be switched also manually via browsing through RZ03 & RZ04. Else you can just want for the time so that your SAP Application does the switch when time comes. The switch log can also be verified via SM21
I also agree with s.sriram. There is no restart needed on making any changes in SAP operations mode.
Refer to below link it clearly says no restart needed.
"You can define operation modes to suit specific system requirements, for example, to provide additional dialog or background processing resources during a particular period of time without having to restart the system."
Just FYI only. (It all depends on your requirements)
We can add operation modes like day time and night time.
"Day time" modes usually have more dialog work processes and less background work processes "Night Time" mode has more background work processes and less dialog work processes. Over all this will also improve performance of the system.