I have a sample Jenkinsfile is here:

pipeline {
    agent {
        label 'master'
    }
    
    stages{
        stage('df'){
            steps{
                sleep 199999
                echo "df"
            }
        }
    }
}

I execute the safeRestart once above pipeline was running.

Expected: Jenkins will restart when the job is completed.
Result: Jenkins restart immediately

Jenkins ver. 2.150.3

The URL is http://localhost:8080/safeRestart