Shatner is the opposite of method acting.
Instead of asking "How can I become this character?" he asks "How can this character become me?"
Disagree.
Method acting, known as the Method, is a range of rehearsal techniques, as formulated by a number of different theatre practitioners, that seeks to encourage sincere and expressive performances through identifying with, understanding, and experiencing a character's inner motivation and emotions.
He does have a live theater background as actors from his era commonly had. Live theater emphasis what could be called "over-acting" but it's necessary in a live performance which he had experience in.
It's the live theater experience that defined the way he played Captain Kirk. He's playing him as if it's a stage production. While some stage actors do dig into method acting, it's a very different thing than the traditional hammy, loud approach. The DDL as Lincoln thing is a good analogy, and at no point does DDL ever think "how should I do this." He just does it because he
is Lincoln. Shatner, by his own admission, was always looking at how best to portray Kirk in any given scene, which is exactly the opposite of the method. Owing in part to the fact that they were doing something kind of new on TV, and nobody was entirely sure how it should be presented. He never
was Kirk.