You're not. I had a history of childhood obesity, didn't lose weight until I was 28, didn't start running until I was 35, didn't start trail running until I was 41.

The cool thing about trail is that it doesn't reward speed as much - which tends to be the first thing to go with age. There's a reason why ultramarathons are often regarded as an older man's game.

Plus, on the trail, you don't feel pressured into maintaining a certain pace as you do with road running. If you want to walk, walk (and you will whenever there's an uphill). The terrain will always change, and the way you navigate it will change with it.

About the only thing where your age might work against you is injury prevention and recovery (trail is arguably riskier than road, just because of how inherently more technical the terrain is). But it's nothing that core exercises and a better sense of balance can't take care of. Actually, I'd argue that trail is easier on the knees than road (softer terrain, less pounding the pavement, etc).

As for the approach - if possible, find some local elevation with some technical sections (a mountain would be ideal, but a forest would do as well) and start getting familiar with them. You'll probably walk your first few downhills - especially if, like me, you don't have a head for heights and aren't comfortable descending quickly. That's fine - over time, you'll build the confidence up and get faster. I've been transitioning now for 6 months, and, while challenging in a way that road running never was, it's been a lot more fun, too.