@Senthoori Sivakumar (Digital)
I will suggest you first to disable scheduled synchronization by running the cmdlet
Set-ADSyncScheduler -SyncCycleEnabled $false.
Close the Synchronization Service and go to the services to restart it again
Then you can enable the scheduler again with below cmdlet.
Set-ADSyncScheduler -SyncCycleEnabled $true
Thank you Bouba88 , i tried that and its the same error : it says unable to stop when the connector is in running state.
Hence we restarted the Microsoft Azure AD sync and that solved the problem,
thanks all !!