Some children are catnappers I think. My DD from about 12 weeks was a catnapper. I tried everything, took away her dummy, introduced a nap routine, got blackout blinds, white noise!!!! I always tried to resettle!!! So much work
In the end I went to Tresillian and the key was to get her early on at the first tired signs (her tired signs are very subtle - when I take her for a nap know people will stare and ask why as she doesn't act tired at all, just gets slightly more quite - and then hyper - that is when I have missed it!). Even then she was inconsistent, somedays sleeping like a star, others needing resettling and still others refusing to sleep more than 45 mins at a time.
Since 7 months she has been better (now 10 months) but every now and again she has a bad few days. To be honest I feel like she would have got here without all the work! So my advice is get in early and don't miss those tired signs, and otherwise go with the flow - your baby will eventually sleep longer in the day all by them self!!!