A question regarding MS Word

I do get riled at myself for having to request assistance knowing
full well that the solution is unquestionably going to be a simple oneŠ
When I'm typing a letter, or just typing something, somehow the entire
left side of the page just disappears. I then have to go down to the
bottom of the page, grab the blue bubble and drag it to the left -
sometimes twice because it jumps back to the right, again. How do I
prevent that from occurring for once and for all?

Thank you so much,
    Edith B