Sometimes it's not about how to steps and checklists. If walking into the room makes you want to scream and hide (which happens to me a lot ) the only thing on your checklist will be "RUNAWAY!" So my first tip is: adjust the environment. Turn on music you like, adjust the curtains so the light is just right, light a scented candle, make yourself snacks to have with you. Invite someone over to hang out while you clean. (If you don't have someone to invite, there are videos on YouTube where you can clean along with someone as they tidy a room in their house.)
If walking into your room and seeing all the clutter everywhere is way too overwhelming, don't be afraid to shove everything into one corner, pull out the few things you're going to work on and turn your back to everything else. You can even pull five things out of your room and work on them elsewhere.
Tip number two: Cleaning up isn't always the first step. While some people might call it getting distracted, sometimes for my AuDHD brain the first step is to just sit with my things. I look around the room and tell myself "these things aren't junk, these things aren't clutter, these things are bits of my life." Then I look around at the piles of things I can currently see and think about what part of my life they belong to. Then I get up and leave the room. The next time I come in I don't feel nearly as overwhelmed so I can work on the first layer.
Also banning yourself from your room isn't a bad practice. If you know that you're just going to mess it up before you finish cleaning it, ban yourself from being in there until it's done. I've done it lots of times. (it helps to plan your outfits for your cleaning week and have them in a different room.) Just don't avoid it all together.
Lastly, while I know sometimes all we want is for someone to just tell us what to do, I think it's very important to say that you have to find the thing that works best for you at the moment. If you try one thing and it doesn't work, don't give up, try a different thing. Also the same thing might not work forever so be willing to switch up your efforts. Lately I've found that checklists and phone reminders help, but in the past setting a music timer was a good thing. Find a way to keep your mind engaged whether that be only cleaning up the green objects one day or completely organizing your bookshelf. You don't have to do it the way other people do it. You are uniquely you. This may not be helpful and I know you might be being pressured by someone else to get it clean , but you've got this. Just don't give up.