I agree with find something you enjoy, or at least something you don't actively hate. That way you won't dread it and talk yourself out of it.
I have realised that working out at home with weights and youtube videos is the only thing I really stick to, and have strangely started to enjoy. Running on a treadmill would drive me insane, so I don't do it, I do brisk walking in a lovely park for cardio, does me fine. If you prefer being part of a class, or need a personal trainer shouting at you to get motivated then do that.
I sometimes have days where I lie to myself and say I'm just going to do 10 minutes, it's better than nothing. I usually end up doing far more than that, but it's a good way to get started when I'm not feeling up to it.
Also, if you have a bad day or week (like I'm having this week) and life gets in the way, don't beat yourself up, but don't use that as an excuse to give up either. Just stick with it, doesn't have to be perfect. Consistency over time will give you the best results.