The construction poner(se) a + infinitivo, prevalent in spoken Spanish, is used to mean to begin/start doing [something], to get something/someone to do [something], to set about doing [something] or to get on with [something].
This verb can be used as either a reflexive verb or a transitive verb.
1. Ponerse a + infinitivo
Read and listen to these examples:
In the examples above, ponerse a + infinitivo suggests the beginning of an activity at a specific moment, usually as an unexpected action.
It is also commonly used to talk about the weather in an impersonal way, as an unexpected action:
De repente se puso a llover.
It suddenly started to rain.
¡Se ha puesto a nevar!
It has started to snow!
2. Poner + (algo/alguien) + a + infinitivo
In the examples above, poner + (algo/a alguien) + a + infinitivo suggests that the subject of the sentence begins to do something. This time it is not reflexive but rather has a direct object.
Notice how in the last example above, the object refers to people (los niños), in which case the conjugated verb (poner) is followed by "a".
Learn more about these related Spanish grammar topics
Examples and resources
Q&A Forum 1 question, 1 answer
Se va a poner / va a ponerse
Yes, you can also say "va a ponerse a limpiar"; equally correct.