It is not choosing the same Entry Node each time. Instead it is getting information about the state of the Tor Network.
Before Tor can connect to Entry nodes, it has to find out about what nodes are on the network. It does this by downloading the consensus from a few fixed computers. Because this step has to happen without any other Tor information being available the IP addresses of these select computers are hard-coded into Tor. After it has downloaded the consensus over the regular internet, it will then select an Entry Node at random to begin forming secure Tor connections.