"Think" is intransitive in your examples, though it can also be transitive when it is followed by an object.
When it is followed by a preposition phrase or a that clause it is intransitive:
(1) Let me think for a moment. (intransitive)
(2) I was thinking of someone else. (intransitive)
(3) She thought that he was unreliable. (intramsitive)
But when it is followed by a noun or noun phrase object, it is transitive:
(4) He thought nice thoughts about him. (transitive)
(5) She was thinking bad things. (transitive)
(6) He thought her unreliable. (transitive)
