Remote server randomly hanging on ssh login

I'll try to ssh into the server

ssh name@box-a

At which point I'll usually be prompted for a password and then it logs me in.

Sometimes though, when I try to ssh in it just hangs after I press enter and does not allow me to enter my password and access the server. There are no error messages, it just hangs. This issue occurs for all users. The issue fixes itself if we restart the server.

ssh -vvv name@box-a

returns

OpenSSH_6.2p2, OSSLShim 0.9.8r 8 Dec 2011
debug1: Reading configuration data /etc/ssh_config
debug1: /etc/ssh_config line 20: Applying options for *
debug2: ssh_connect: needpriv 0
debug1: Connecting to box-a [box-a] port 22.
debug1: connect to address box-a port 22: Operation timed out
ssh: connect to host box-a port 22: Operation timed out

What should I do next?