public class StartBoot extends BroadcastReceiver {
    @Override
    public void onReceive(Context context, Intent intent) {
        if(intent.getAction().equals(Intent.ACTION_BOOT_COMPLETED)){
            Intent intent1 = new Intent(context,MyService.class);
            context.startService(intent1);
        }
    }
}

<application
    android:allowBackup="true"
    android:icon="@mipmap/ic_launcher"
    android:label="@string/app_name"
    android:roundIcon="@mipmap/ic_launcher_round"
    android:supportsRtl="true"
    android:theme="@style/AppTheme">

    <activity android:name=".MainActivity">
        <intent-filter>
            <action android:name="android.intent.action.MAIN" />

            <category android:name="android.intent.category.LAUNCHER" />
        </intent-filter>
    </activity>

    <receiver android:name=".StartBoot">
        <intent-filter>
            <action android:name="android.intent.action.BOOT_COMPLETED"/>
            <category android:name="android.intent.category.DEFAULT"/>
        </intent-filter>
    </receiver>

    <service
        android:name=".MyService"
        android:enabled="true"
        android:exported="true"></service>
</application>

W/BroadcastQueue: Permission Denial: receiving Intent { act=android.intent.action.BOOT_COMPLETED flg=0x9000010 (has extras) } to com.google.android.apps.docs/.app.NotificationChannelReceiver requires android.permission.RECEIVE_BOOT_COMPLETED due to sender null (uid 1000)