Hi! Good question. Here's my experience...
I was never into athletics as a kid, but was active and relatively healthy so every so often I'd get a bug to start a real fitness regimen. I joined an athletic club in my early 20's for a while... then again in early 30's... and again in late 30's.... (see a pattern?) and finally came to the conclusion I just wasn't a club person. Too many sweaty people, too many rude people, too much this, too little that, I don't like doing classes... blah blah blah. THEN last year at 42 I finally found what motivates me -- peer pressure! A friend talked me into signing up for an 8-week boot camp class, outdoors in the cold, at 6 a.m. My husband laughed. But I liked the tough but low-tech workout (all outdoors, NO equipment, different every day) and knowing there would be roll call (and small prizes for perfect attendance) made me look forward to going. I thought I'd just do it for 8 weeks and that would be the end, but after about 6 weeks I was hooked and have been going for 14 months now. Depending on the season, there are 30 to 60 people in our class, all working out together on local streets, a nearby college campus, empty tennis courts, city parks, or even a parking garage if it's raining or snowing.
I had never had consistency in my approach to fitness before, so I had never really experienced what it's like to be in all-around good shape with muscle tone and endurance and clothes that fit so much better. Wow!! That's motivation in itself and now I can't imagine stopping. Sure, I have more energy some days than others, but by and large it is integrated into my life and I feel icky when I don't get my workout in. And I only work out three times a week! I also love knowing that I could work out more days per week and get even more benefit. In fact, my husband and I heard about a half marathon training group from somebody at boot camp, and we're going to join that group in the spring. Our longest race has been 12k so we're really excited to train for something longer.
I don't know if joining a group (friends or strangers) would help you, but it sure helped me so if I could offer one suggestion, that would be it! It's a good way to meet people and network as well. Good luck.