'Sort of' can be used as an adverb (usually modifying an adjective) with a meaning similar to 'a little bit', 'to a moderate degree' or 'somewhat':
- She's sort of pretty.
- It's sort of cold outside today.
- That test was sort of difficult.
Adding the word 'some' changes things. This phrase is used to modify and categorize a noun. The word 'some' tends to indicate that there is a degree of uncertainty or lack of precision in the categorization:
- He is some sort of nut.
- I think that's some sort of reptile, but I'm really not sure.