The first workout I ever did consistently was just 20 minutes long. I would grab a pair of 15-pound dumbbells and do a mishmash of exercises in a circuit. Squats, lunges, push-ups, planks, side planks—the whole shebang. I loved that it was short and that I could do it all in the same little corner of the gym. There was less chance that people would look at me.
Most importantly, I knew how to do it. And I was absolutely convinced that it would work.
Here's the thing, though: It was a terrible workout! Knowing what I know now, it had a lopsided mix of exercises and was way too focused on getting you tired (instead of actually getting you fit). At the time that didn't matter because I was so sure it would work.
I pulled that workout from some random corner of the internet. It was by one of those fitness personalities who could basically lie around eating chips all day and still look great. It didn't work on its own, but it got me to the gym.
By the time I realized that the workout I was doing wasn't effective, I had developed a regular gym habit. The gym was less scary and I was more confident. I just found a better workout and plugged it into my workout time. I'm not saying that you should find a bad exercise routine to follow, but if you want to stop skipping workouts, I suggest learning a simple routine inside and out. It takes out the intimidation factor.
There are dozens of places to find routines and instructional videos. On my own journey I found success stories really motivating because I was a little guy trying to gain weight—so I looked up before-and-after pictures of people in the same situation. If you find success stories from people like you, it's evidence that you can achieve your goals. If you want to change programs once you've got a habit going, that's totally fine too.
Moral of the story: Pick something and stick to it. When you're convinced something will work, it starts working—even if "working" means being consistent. Good luck!