I turned 50 a few weeks ago, having left H in the summer and moved to a city 3 hours away that I'd only visited briefly before, and where I knew no-one. Am planning an access course next September, with a view to a specific degree in a subject I've always been really interested in. And another house move in a few months. I do have a job though, so it's potentially been easier for me. Youngest DC went off to uni in September, I had a perfect storm of mid life crisis/lockdown separation/empty nest stuff going on.
Re weight, I'm half way through my target weight loss, once I get there I intend to completely overhaul my wardrobe (I'm fancying the little dresses and boots combos I used to wear back in the day, maybe not quite a short as they used to be though!).
OP, pick something you want to change, and do something about that. I echo volunteering, that would give you a reference for a job application, as well as giving you a confidence boost. Or do a get fit/lose weight focus. Or see where your relationship could be improved. Just pick one thing, and do that for a couple of months, see how it goes. Then pick another thing and add in working on that.
But yes, it's perfectly possible to start over/start again, I hadn't put into words how I'd been feeling for a very long time, and it was only when I did, that I twigged I had a good thirty years left, and I didn't want to waste them as I'd been doing for the previous fifteen. I'm really excited about the possibilities in my future, I might meet someone, I might not (and if not there's Lovehoney 
), but everything I do now feels like an adventure, even just eating what I want to eat, when I want to eat it, without having to factor in other people's tastes and moods. Grab the next phase of your life by the scruff of its neck, and go for it 