As another 'heavier rider' I'd suggest looking at whether you can lay your hands on a secondhand German bike. They tend to make their bikes more robust for the fuller figured... the Dutch do as well.
Forget carbon frames - look for steel or (at a push) aluminium.
Look for a bike with wheels with a high spoke count. 32 or more would be best - I'd suggest 28 as a minimum. Anything less than that and you may find yourself spending a lot of time getting spokes replaced.
Others have mentioned saddles and padded shorts. This very likely will be an issue and will be affected by the style of riding. My personal experience was that a slightly wider saddle, with padded shorts and chamois cream, was the way to go.
The key is frequency. It's about how often you ride rather than the distance - it's better to do regular short distances than infrequent long distances, and as you go on you'll find those short distances get longer naturally.
If you get hooked and decide to go down the lycra route, you'll find that most of the manufacturers don't really cater for the larger rider very well.
Decathlon's larger sizes are quite good and there are specialist suppliers, such as
Fat Lad at the Back (whose stuff is really good quality and fun).
More importantly, check in here for added encouragement and support. You may even find someone to ride with - cycling with someone can make it easier.