The wind billowed
Would i say "the wind billowed" as "el viento se hinchó"? Is it reflexive here?
5 Answers
I don't think the wind itself billows. It causes other things to billow:
The sails billowed in the wind. Granny's underpants were billowing on the washingline, in the strong wind.
What about - el viento se ondulaba?

What about - el viento se ondulaba?
With literature almost anything is possible, but it would make more sense to say something like "El viento soplaba haciendo que se ondularan los arboles / las flores".
I would say:
El viento se hizo más fuerte.
El viento comenzó a soplar más fuerte.
El viento tomó fuerza.
Yes, you would use reflexive, but "el viento se hinchó" sounds strange. Maybe " el viento aumentó" or "se incrementó la velocidad del viento" etc.