ML.NET prediction speed improvement for object detection

Question

I've created a ONNX model for Object Detection with Visual Studio and ML Model Builder, using VOTT to define the 4 objects I want to detect.

I'm testing the model as explained in the tutorial, and it works well, result is ok:

        var sampleData = new MLModel1.ModelInput()
        {
            ImageSource = @"C:\Data\sample1.jpg",
        };

        //Load model and predict output
        var result = MLModel1.Predict(sampleData);

Problem is it takes 5 seconds (10 seconds on first run, 5 on the following ones). sample.jpg is a 700x400 pixels image, 85kb, the computer is a Intel i7 2.9GHz.

Why it's so slow? Am I doing something wrong or this is the speed I should expect? Here's the image, the objects to detect are the REF, LOT, the hourglass icon and the factory icon.

Is there any other technique I could use to have a faster detection of these objects?

Thanks