No option Central Admin to start it.

Probably, you are at "Services in Farm" page.
Try to navigate "Services on Server" page - Start option should be there.

You can also start it from SharePoint Management Shell, smth like:

$srv = Get-SPServiceInstance | ? { $_.TypeName -eq "User Profile Service" -or $_.Service -eq "UserProfileService" }; $srv | % {Write-Host $_.Server $_.Status; if ($_.Status -ne "Online") {Start-SPServiceInstance $_}; } 

Then, got to Monitoring - Check job status - filter by Job Definition: "User Profile Service Application - User Profile ActiveDirectory Import Job" and make sure that this task is completed successfully.

No option Central Admin to start it.

Probably, you are at "Services in Farm" page.
Try to navigate "Services on Server" page - Start option should be there.

You can also start it from SharePoint Management Shell, smth like:

$srv = Get-SPServiceInstance | ? { $_.TypeName -eq "User Profile Service" -or $_.Service -eq "UserProfileService" }; $srv | % {Write-Host $_.Server $_.Status; if ($_.Status -ne "Online") {Start-SPServiceInstance $_}; } 

Then, go to Monitoring - Check job status - filter by Job Definition: "User Profile Service Application - User Profile ActiveDirectory Import Job" and make sure that this task is completed successfully.

After that, look at the ULS logs. You can filter it by rows containing UserProfileADImportJob or Category: User Profiles. There will be hints to the root cause.