Intent intent= new Intent(this, NotificationListener.getClass()); startService(intent);

public class NotificationListener extends Service {

    private SharedPreferences sharedPreferences;
    private SharedPreferences.Editor editor;

    public NotificationListener() {
    }

    public static final int JOB_ID = 0x01;


    @Override
    public IBinder onBind(Intent intent) {
        throw new UnsupportedOperationException("Not yet implemented");
    }


   @Override
    public int onStartCommand(Intent intent, int flags, int startId) {
        sharedPreferences = PreferenceManager.getDefaultSharedPreferences(getApplicationContext());
        editor = sharedPreferences.edit();
        final Handler handler = new Handler();
        handler.postDelayed(new Runnable() {
            @Override
            public void run() {
                Post post = (Post) new Post().execute("тут url", "user_id=" + sharedPreferences.getInt("userId",0));
                try {
                    ShowNotification(post.get());
                } catch (ExecutionException e) {
                    Log.i("MSG","SOMETHING ERROR " + e);
                } catch (InterruptedException e) {
                    Log.i("MSG","SOMETHING ERROR " + e);
                }
                handler.postDelayed(this, 10000);
            }
        }, 0);
        return START_STICKY;
    }



    private void ShowNotification(String result) {

        JSONObject dataJsonObj = null;

        try {
            dataJsonObj = new JSONObject(result);
            if (dataJsonObj.has("notification")) {
                JSONArray getNotify = dataJsonObj.getJSONArray("notification");
                String content = "";

                for (int i = 0; i < getNotify.length(); i++) {
                    JSONObject notify = getNotify.getJSONObject(i);
                    content += notify.getString("content");

                }
                Intent notifyIntent = new Intent(this, MainActivity.class);

                notifyIntent.setFlags(Intent.FLAG_ACTIVITY_CLEAR_TASK | Intent.FLAG_ACTIVITY_NEW_TASK);
                PendingIntent pendingIntent = PendingIntent.getActivity(this, 0, notifyIntent, PendingIntent.FLAG_UPDATE_CURRENT);

                NotificationCompat.Builder builder = new NotificationCompat.Builder(this);

                //builder.setContentIntent(pendingIntent);
                builder.setContentTitle("У вас новый заказ!");
                NotificationCompat.BigTextStyle bigTextStyle = new NotificationCompat.BigTextStyle();
                bigTextStyle.setBigContentTitle("У вас новый заказ!");
                bigTextStyle.bigText(content);
                builder.setContentText(content);
                builder.setStyle(bigTextStyle);
                builder.setAutoCancel(true);
                builder.setDefaults(Notification.DEFAULT_SOUND);
                builder.setWhen(System.currentTimeMillis());
                builder.setSmallIcon(R.mipmap.ic_launcher);
                builder.setContentIntent(pendingIntent);
                Bitmap largeIconBitmap = BitmapFactory.decodeResource(getResources(), R.drawable.logo);
                builder.setLargeIcon(largeIconBitmap);
                builder.setFullScreenIntent(pendingIntent, true);

                Notification notification = builder.build();
                NotificationManager notificationManager =
                        (NotificationManager) getSystemService(NOTIFICATION_SERVICE);
                notificationManager.notify(1, notification);
                startForeground(1, notification);
            }
        }
        catch (JSONException e) {
            e.printStackTrace();
        }
    }




}

<uses-permission android:name="android.permission.RECEIVE_BOOT_COMPLETED" />
    <uses-permission android:name="android.permission.QUICKBOOT_POWERON" />
    <uses-permission android:name="android.permission.REQUEST_IGNORE_BATTERY_OPTIMIZATIONS" />
<service android:name=".NotificationListener"></service>