Talking about these two specific phrases "Voy en camino" and "Estoy en camino" mean exactly the same.

¡Muchas gracias!

Both phrases mean the same but we always say in these cases"estoy de camino a.."

Those two phrases DON'T mean the same, they are both incorrect xD. "Voy en mi camino" means " I am moving (walking, driving, running,etc...) on my road" and "Estoy en mi camino" means "I'm on my road" as if you were staying there. You don't need to use "my", I mean, in English You have to say "I'm on my way" but in Spanish We don't need to use It because the verb gives us all the information that We need, Furthermore, It means that you own a road(If you use "mi"). "Voy" means "I am going". By the way, It sounds more natural to say "Voy de camino" instead of "Voy en camino", You can use both but the first one is more usual.