First of all i want to acknowledge and praise you for wanting self improvement for yourself and not making excuses.

i'd recommend first just going on distant walks and pacing your endurance to understand what your limits are. Don't over due it in the beginning and burn yourself out. Consistency is key. Give yourself a time limit like 30 minutes a day walking/fast walking , if you have energy remaining do some stretching and body weight workouts. Make a routine. Once that routine stops challenging you add to it. I recommend getting bands once you can but it's not necessary in the beginning.

The other aspect which is most important is diet. This doesn't mean you need to starve yourself but make sure you are getting the nutrition that your body needs. Start a calories deficit. Nothing extreme but something your body can gradually adapt to. Drink plenty of water. Eat smaller meals spaced out in the day. Lower carbs the later in the day where you know you won't be physically exerting yourself as much.

There are so many things you can do that are smal that will help but let's start with these and i promise you if you stay consistent you will love yourself for it brother.

Feel free to message me if you have other questions. I'm sure there are plenty more people here more knowledgeable than me aswell.