I started out earlier this summer with a Roadmaster MTB from Walmart that was my son's but it was ill fitted AND it beat my hands up terribly. I have carpal tunnel and it made it nearly impossible to ride ANY distance.
I got my new Trek Navigator 50 July 27 and I have over 700 miles on it already.
I'd go to your LBS and test ride the Navigators. Jimmy at Bike Line in Carmel showed me the Navigator and I couldn't believe how comfortable it was.
Good Luck!