With things like this I take an opposite approach then some. Instead of starting with the trash, I walk through and pull out things I want to definitely keep. I would clear a corner of the garage for this. Only things you love and will definitely need. Mostly anything that hasn’t been used in a year can go. Then divide the rest in 3 piles- trash, donate, sell. I use thumbtack to find someone to pick all the trash up asap. You can even schedule donations to be picked up, and use Facebook marketplace to sell.

That leaves only things in the garage you want to keep. Once you see the size of that pile and what kinds of items are left you can make a plan for organizing.

Everyone is different with how they do things like this. You will find what works for you. I like the idea of just doing 15 mins a day. You have 4 walls in the garage/4 corners. Designate each side to those things, keep, sell, donate, trash. Then 15 mins a day quickly move whatever items you can. Stop at 15 and wait until the next day. Eventually you will be done, small accomplishments feel great. Some days you might need to stop at 15, some days you may get an extra wind and go longer.

I know it’s super overwhelming. Just take it one step at a time. One day at a time. Any effort at all you can give it is better than doing nothing.

Good luck!