Sometimes, as an adverb, is one word. However, if you are using 'some' to mean 'a few' and 'times' to mean occasions, they are two separate words.
For example:
'I sometimes correct people when they spell 'grammar' incorrectly. But there are some times when I don't. On these occasions, I give the person an example of the correct spelling in the hope that they will work it out for themselves.'