Normally 'now' just means 'at the present time', and it can be placed in those positions you mention. A common example from weddings: "I now pronounce you man and wife. You may (now) kiss the bride." "I used to like sarcasm; I now find it tiresome." (or you could say "now I find it tiresome") "I will now go to bed." In questions in common speech, sometimes 'now' has another meaning, but this usage is not as common: "One day I'll be president!" "Oh will you now?" ('now' could mean "I don't believe you", "you are really quite impressed with yourself", or, if speaking to a child, could be kindheartedly playing along)

If you're asking for sentences that use the phrase "I will now", here are some: I will now walk to the store. I will now play a game. I will now smile and wave. I will now buy this shirt. I will now open the letter. I will now push the button. I will now begin the test. I will now drink some tea. I will now use the microwave. I will now wash the dishes. I will now clean the house. I will now sing the song. I will now add a comment. I will now answer your question.

"I am going now to my work " you talk about something you are doing at this moment not something you would do in the future