Would thae placement of 'sjelden' put any emphasis on any part of the sentence? In English, one would say: I seldom see my uncle. But can't do that in norsk so....does the placement of 'sjelden' after the verb underscore that I seldom SEE my uncle (but may talk to him often, etc) or if after 'onkelen min' suggest that i don't see HIM often but see others more frequently. Or am I making something out of nothing? (: Takk!!
In English, the present continuous tense (ex. I am going to the doctor) is usually used to talk about something happening NOW. The present tense (I see) is used for things that happen often (ex. I go to the doctor every week). Since seeing your uncle is something that you often do or don't do and it is not something happening right now, you must say "I rarely see my uncle." Saying "I am rarely seeing my uncle" doesn't make sense in English.
Bonus tip: the senses (hearing, seeing, smelling, etc.) are rarely used with the present continuous tense (ex. I am hearing beautiful music) and almost always with the present simple tense (ex. I hear beautiful music).