Most of my typos (no really, honest) is due to the key board not being able to keep up with my typing. I often get two Capital letters at the start of a word. I'm pretty sure that given there are usually only two, it's not the I haven't pressed the key. Annoyingly, although the editor (this one is particularly good at auto correct) will put the usual mistypes (OK just plain bad speellinng) right it doesn't auto correct WHere or However or JUSt in case.
What they often do is notice a badly spelt word and stick something in there instead that isn't the word you meant. When you read it through the correction looks like a good word, but can easily be out of context making the sentence nonsense.
Now there's is a strange thing - When I typed that However above I deliberately had an 'O'. But look at it now. It's been put right - what's going on?