Do the Vedas speak of Brahman as a being that is able to think and perform actions? Or is Brahman more like an inanimate thing, except immaterial?
In the Vedas it is stated that the Brahman has entered our bodies and has established itself/himself in our minds.
eko ha devo manasi pravishtah ||
The sole God has established himself in the mind. Atharva Veda 10.8.28
shariram brahma prAvishat ||
Brahman has entered this body. Atharva Veda 11.8.30
Now, anything, which is not endowed with consciousness, can not perform the above mentioned acts. So, as per Vedas the Brahman is conscious.
Similarly, the Upanishads describe the Brahman as seeing, as thinking and as desiring.
From Aitareyopanishad' 1st adhyAya's 1st Khanda we have:
AtmA bA itadmeka evAgra Asit |
NAnyat kinchana mishat |
Sa ikshat lokAnnu srijA iti ||
Prior to creation, everything that was there is that AtmA alone (or Brahman alone). Nimesha etc units of time and no other activities prevailed then. Then, that AtmA thought thus (or resolved thus) --- I will create (or give birth to) the worlds (lokAnnu srijA).
Here, the relevant word used in the original text is "Ikshata" which is derived from the word "Ikshana" meaning "to see". However, here, overall the meaning is that ----- The Brahman saw, then contemplated on the situation (that he is alone) and then he desired to create many from one.
So, again, these acts of seeing, thinking about a situation, understanding that he is alone and finally desiring to create can not be performed by beings which are not endowed with consciousness.
In general, in the scriptures the Brahman is mentioned as Sat+Chit+Ananda, where the Chit is referring to the consciousness part.
Note that there can be plenty of more references which can be used to prove the same.
Brahman is without form, and therefore the attributes of Brahman are beyond our understanding. In the Bhagavad Gita though, it is made clear that Vishnu is Brahman, ergo all properties of Vishnu are the properties of Brahman. Vishnu is a kind of personification of Brahman.
Brahman does not "think", because thinking is a biological function. Brahman has no mind, but does have intellect. The difference between mind and intellect is that mind is what calculates and sums up options but the intellect is a state of knowing without thought.
Hope this makes some sense.