In Spanish we use this verbal structure (known in grammar jargon La perífrasis verbal) to express "To begin/start doing[something]".
Empezar/comenzar (conjugated)
a +
Infinitivo
Have a look and listen to the following examples in different tenses:
Yo he empezado a bailar esta semana.I started dancing this week.
Manuel comienza a gritar cuando no lo escuchas.Manuel starts shouting when you don't listen to him.
Nosotros empezaremos a estudiar alemán la semana que viene.We will start studying German next week.
Ellos comenzaron a construir las casas ayer.They started building the houses yesterday.
Notice how the preposition "a" always follows empezar/comenzar. In Spanish, unlike in English, after "a" we do not use a gerund (-ing form) but the infinitive.
Marcos empieza a trabajar hoy.
Marcos empieza a trabajando hoy.
Marcos begins/starts to work today.
See also:
Manuel comienza a gritar cuando no lo escuchas.Manuel starts shouting when you don't listen to him. Ellos comenzaron a construir las casas ayer.They started building the houses yesterday. Nosotros empezaremos a estudiar alemán la semana que viene.We will start studying German next week. Yo he empezado a bailar esta semana.I started dancing this week. 
