I'm just curious. I like to think that I am decent with grammar, but this has me puzzled.
Which is the correct way to arrange my sentence?
"I can sometimes..."
"I sometimes can..."
As far as I'm concerned, there's no "correct" way here...
Both of those, plus - what I would argue as the most popular option - "Sometimes I can" are all OK in my book.
- I can sometimes see the future but it's not working today.
- I sometimes can eat an entire pizza alone.
- Sometimes I can spell complicated words without needing the spellchecker!
A lot of the time, I'd say that the version you choose will depend on the word you want to emphasize.
Of the three, I'd say that the first and third are the more common constructions... which this Ngram seems to agree with.
The answer is rather complex.
There are some rules that regulate the position of an adverb of frequency, such as: sometimes, often, occasionally, always etc.
subject aux/be adverb main verb object/place/time I *often* go swimming in the evenings. He doesn't *always* play tennis. We are *usually* here in summer. I have *never* been abroad.
but real usage is different for each one of them. One first distinction must be made between adverbs of frequency that can be used at the beginning (less frequently at the end) of the sentence, an adverbs that cannot.
In the example in question there is a modal verb can which functions as an auxiliary verb and therefore the correct position of the adverb should be between the aux and the main verb, as in this quote from Noel Coward:
"I'm not a heavy drinker, I can sometimes go for hours without touching a drop."
You can *never* leave I can *usually* drink I can *sometimes* go
it is an exception to the rule, since it has a peculiarity of its own: it must be placed at the beginning in a negative sentence, you say:
but, if you want to use sometimes in all these examples, you have to place it right at the beginning. You don't say:
"I don't sometimes go to church", "I have not sometimes gone..", "I can't sometimes go for hours", but you say: "*sometimes I don't/have not/can't..."
Any other position, including the one suggested by the general rule, is felt as wrong.
The non-negligible presence of the incorrect I sometimes can...." in the ngram quoted in another answer is due to the fact that it is quite correct in an answer: "Can you go for..." - "Sure, I sometimes can!" If you consider it a modal verb followed by another verb, the result of the * ngram is different and gives "Not found" for the wrong form, and the other two are on the same level.
The representation of the three variants in the other ngram is misleading, since it suggests all of them are correct.
Lastly if you search for another adverb occasionally in the truncated, ambiguous form : "I occasionally can..." you get "Not found", which confirms, in a way, the peculiarity of sometimes
"Sometimes" is bad toward the middle:
sometimes the fish must have been being eaten for hours
the fish sometimes must have been being eaten for hours
the fish must sometimes have been being eaten for hours
the fish must have sometimes been being eaten for hours
*the fish must have been sometimes being eaten for hours
*the fish must have been being sometimes eaten for hours
the fish must have been being eaten sometimes for hours
the fish must have been being eaten for hours sometimes
McCawley in The Syntactic Phenomena of English gives a theory of adverbs that makes "sometimes" (and all time adverbs) modifiers of V-bar which can optionally be raised to be sentence modifiers. That predicts that all the patterns I've just listed should be acceptable. IMO, here, and overall, McCawley's theory doesn't work very well. I have my own theory of adverbs which, unfortunately, doesn't work very well to predict facts of adverb placement, either. It's a difficult problem.