Use of volitional form

MNN31-2

The volitional form is used in plain style conversations and also to express intentions.
This form is also used when talking to or about self to mean I will.
今日は早く帰ろう。
明日は何をしようか。

to express what the speaker is thinking of doing, using ~と思っています

思っています is the continuous form of 思います and it indicates that the speaker has been thinking about doing something for some time.
For the third person, it has to be in progressive form.

鈴木さんは新しい靴を買おうと思っています