Rule reminder
Register determines which periphrasis is appropriate. 'Solere + inf' and 'essere solito + inf' are formal/literary. 'Venire + pp' is preferred in journalistic/bureaucratic writing over 'essere + pp'. 'Mettersi a' is more colloquial; 'iniziare a' can be more neutral/formal than 'cominciare a'.
FORMAL academic writing: 'The phenomenon tends to occur in winter.' Best option?