Some people don't have any of these blocks (or at least, none strong enough to stop them). These people are the ones who say "just do it", because for them, the only trick is to stop thinking and roll up their sleeves. But many people can't "just do it".
Some people only have one or two things blocking them. They fix those things, and suddenly they become highly productive. These are the people who will go around saying that they have finally found the magic bullet that solves their productivity problems.
Some people have a ton of mental blocks. Often these are beliefs that work as cross-purposes.
For example, it sounds like you have the belief "if someone else makes something that I had the idea for, that's terrible". This pushes the "knot inside you to inarticulately roar". Trick is it's not that you want to work on something cool, it's that you don't want to not have worked on something cool (subtle, but important difference - negative motivation is very poor at driving creative work).
Another belief is "all I want is to get something finished, these things hold me up on things that I know should be almost trivially easy". This one is familiar to me. This conflicts badly with belief number #1, since one part of your brain is telling you you have to get coding, and another part is flashing warning bells telling you that whatever you are doing can't be worthwhile because it's so hard. Result: paralysis.
The good news is you can debug these different blocking beliefs.
I learned most of this stuff from PJ Eby's site: trouble is he uses an offputting sales-letter/self-helpy language, but the ideas are golden. http://pjeby.com/ http://thinkingthingsdone.com/ are your starting points. Email me (isaac@i.saac.me) if you (or anyone else) wants to talk more; I'm thinking of starting a site which communicates some of these ideas.