Thank you for the link. (Here's a better one, same page, but this one opens: Fortune City). The page reads:
The adverb sometimes (note the -s) can occur in three positions: at the beginning of the sentence, at the end of the sentence, and between the subject and the verb.
It should be noted that sometimes is an adverb of frequency, whereas sometime is an adverb of time.
Ex: I sometimes see him in the park.
Ex: I would like to read that book sometime.
In the first example, the adverb of frequency sometimes occupies the middle position of a clause.
In the second example, the adverb of time sometime occupies the end position of a clause.
Does that help?