I have felt exactly as you felt for a long time. The answer that's working for me is really short: look at the problem and look for something really small and say "I could [do x]," and then immediately do x. This gives you the freedom from thinking about the larger thing it is a part of, from thinking about the order of doing things / trying to optimize it. For example, let's say I want to clean up my place. If I look at everything it looks overwhelming, boring, and I think about how I let it get so bad. This is very unmotivating. But I look for a smaller problem: I see a coat on the floor. I say "I could hang that up." So I hang it up. More importantly it gets me moving. Momentum is everything! The mind latches on to unfinished problems. If I throw one can into recycling it's going to look at the next can next to it and will 99% of the time will be compelled to do the next one. Whatever project I've recently worked on will have a much greater chance of continuing.
You can do the same thing with work stuff. I could just open the spreadsheet. I could just open the email I need. I could just log in the box I need. Suddenly I've started working on it and I'm good for the rest of the day.
Look for something really microscopically small to do next. It doesn't have to be optimal, it doesn't have to be the most important, the most urgent, or even that useful. If the task is small enough it slips under the threshold of such evaluations. I think this also gets you into the habit of taking action immediately rather than waiting. But if it doesn't, you can always kick start yourself again by doing anything small. "I could ...."
For me it rarely works. I know, what you mean, sometimes it does, doing one thing makes my body follow with others semi-automatically, without thinking about each one. But most often I just do this one thing and then stop. I can then do another, and another, but each with the same effort as the first one.
Now that you mention it, that's pretty accurate. You do still have to think about each step still; just keep repeating the process of finding a really small thing that is totally doable immediately and do it. The difficulty remains the same throughout, but it would be at a doable level the whole time. On the other hand, I do get excited that I'm actually making progress on something, and I try to get to a point that has a reward.
This is the only thing that's ever worked for me; although even though it's worked, and is trivial to implement, even so it's often not been enough. How can one have a tool that successfully does the job, and yet so often ignore that tool? I don't know. Motivation is a strange beast.
You can do the same thing with work stuff. I could just open the spreadsheet. I could just open the email I need. I could just log in the box I need. Suddenly I've started working on it and I'm good for the rest of the day.
Look for something really microscopically small to do next. It doesn't have to be optimal, it doesn't have to be the most important, the most urgent, or even that useful. If the task is small enough it slips under the threshold of such evaluations. I think this also gets you into the habit of taking action immediately rather than waiting. But if it doesn't, you can always kick start yourself again by doing anything small. "I could ...."