I don't know that there is a best time to shower after a workout, I think it depends on the person.
I don't think it matters too much, as long as you don't shock your body with a drastic temperature change.
Actually, athletes who want to improve their nerves will shower immediately after a workout. While in the shower, they alternate between cold and hot water to improve circulation and nerve reaction.
Not sure if this is for you, but the correct time to shower is all based on what you want to do. If you feel like you are too hot right after you work out, then take some time to cool off. Cool off time is just your resting heart rate, so it varies but shouldn't be too long.