I'm am not sure that I understand your question.
Are you saying that when you type a space,
followed by a lower-case "i", followed by another
space, that Word is not automatically replacing
the lower-case "i" with an upper-case "I"? It is
supposed to automatically replace a lower-case
"I" unless you've deleted that entry in autocorrect.
Check. Do you have "autocorrect as you type"
option unchecked? If so, check it.
Word views a lower-case "i" surrounded by blanks
as a mistake and auto-corrects it to a capitalized "I".
Scroll down auto-correct entries to "hwich" (which
is auto corrected to "which"), and you'll see the "i"
to "I" correction immediately following.
You have options:
1. Delete the current "i" correction entry and replace
"^i^" with a "^I^" entry, where ^ equals a space.
What would you accomplish? Nothing that I can
tell. It's 0305 hours eastern USA, and my brain
has turned to bats---t. <g>
2. Leave the auto-correct entry alone, and
get used to typing personal pronoun "i" as "I".
I heartily endorse option 2. It's so much simpler.
Also, be aware that auto-corrections has an option
to capitalize the first letter of a sentence. You may
want to play with this, too, but I'd leave it enabled.
Good luck.
Uncle Joe