Why did Admiral Kirk refuse to raise Enterprise's shields when the USS Reliant refused to acknowledge its hails?

Was it simply a case of spending too long out of the captain's chair, since he otherwise, would probably have immediately reacted to protect his ship against anything that seemed out of the ordinary and therefore a potential threat?

Or was it a case of him not actually refusing so much as he was still trying to size up the situation? In other words, he must've found it pretty peculiar that the Reliant still wasn't acknowledging hails, and put the ship on yellow alert. Also, Saavik started to quote regulations at Kirk like they were in a training exercise and Spock rightfully dressed her down in front of everyone.