What physical activity do you currently do?
What sports or physical activities have you enjoyed doing in the past, including childhood?
Do you usually cook for yourself or do you eat out?
My general prescription: eat out at most once per week. Cook more or less healthy stuff for yourself the rest of the time (really don't need to try too hard here, you aren't trying to become a fitness influencer or whatever). Find a physical activity that you enjoy and look forward to, then do it every second day. Common "fun" physical activities for adults include vinyasa yoga, rock climbing, martial arts (BJJ, Muay Thai, boxing, kickboxing), or some kind of group general fitness class. Finally, if you have a sedentary job, on the days when you aren't doing your physical activity try to go for a walk around the neighborhood of at least 1 hour duration. This will make you more physically fit than probably 90% of the population.
Regarding a lot of the other advice here: this is a bit of a hot take but going to the gym then putting in earbuds and lifting weights alone while staring at the wall is sad, boring, and lonely. I've lived that life and it fucking sucks. Mattress on floor vibes. Physical activity is an excellent way to connect with others, so choose forms of working out that do that.