SB - acoustic guitars come in various 'shapes' so you should be able to find something comfortable. I started with a 'dreadnought' shape, which is the most common, but always felt a little awkward with it. The next guitar I bought was a 'Grand Auditorium' which I found much more comfortable. Then I bought a Jumbo. Last week I went into a shop and played a dreadnought and it felt fine. There are some slimmer models available as well (Yamaha APX5A and Taylor Big Baby spring to mind)
I guess I am saying that if you can get to a shop and try a few different shapes out, do it. All will probably feel awkward to start with though, so unless one really makes you feel better then just buy the guitar you like the best. In 1/2/3/6/12 months you'll be in a shop trying everything to find your 'step-up' guitar anyway, all you need right now is something that makes you want to play.
It can be really frustrating when you first start, but stick with it, as keeping doing it even when you feel like you aren't getting anywhere is what makes you get better.
Good luck in your search.
I reccomend you buy the best guitar you can afford...My first acoustic was around $200 and I thought it was great...but I had a lot of dificulty fingering chords...and just thought it was me....then I tried a friends Ovation and it just fit better and seemed easier to play...I went out and bought a used for for $600 and what difference. It has a maple neck and to me that seems so much nicer to play...
Then my fingers ached from calloses which happens to every one...but i dropped down to lighter strings and my playing has improved, chords are easier to form and so on...
My point is to try alot of guitars before you buy....cause if you are not comfortable it wont take long for you to tire out and/or become frustrated. I also use a foot rest when i play acoustic..it seems to help my playing alot too....
