I had some Karate and Kung Fu training before I began Aikido in 1986. After my first few Aikido classes...I found walking and chewing bubble gum at the same time a real chore!!!
After a few years of Aikido, the movements always felt contrived....forced....in other words....I could not do them!!
My Sensei then, Len Rose Sensei (God watch over his soul), had the patience of a Saint, and kept after me to not think of the movements as some strange martial arts move, but rather a simple everyday movement. Over the years moving has become less of an effort.
My Sensei now, Bill Gleason Sensei, has deepened my understanding of movement. When I watch Gleason Sensei move with Bokken, I do not see this move or that move, but rather I see one long flowing movement. One I hope to be able to come close to in another decade or so.
When I have my small class with some beginners, I try to make the movement seem like walking and turning when called by a friend. Or assimilate it to a dance step one may have done. Just so the students do not think of the move as some mystical step.
To answer the question,,,,,,
How natural are Aikido movements to me?
Some are as natural as walking now.....
When in the past they were most difficult.
A very good question.....one that has made me think.......