Why is the expresso shots not hot?

What temperature are your shots coming out at? To accurately measure this you need to place an instant-read digital thermometer directly in the stream of water coming from the brewhead (leave the portafilter off); temperature should be around 200 F. If considerably cooler you may have calcium buildup in your boiler that's preventing the machine from heating properly, and in that case you should descale it with Durgol or other citric acid-based descaling agent.