I have an old headless server running Linux version 2.6.32-5-686 (Debian
2.6.32-48squeeze1) (dannf@debian.org) (gcc version 4.3.5 (Debian 4.3.5-4)
). Recently, when I log in using ssh the terminal window freezes for a few
seconds, then usually comes back. The command line stops printing the
characters I am typing, the cursor stops blinking, and then after a few
seconds, it comes back. This happens every few minutes, so it is becoming
rather annoying.

When I check the disks, I get
# df -h
Filesystem            Size  Used Avail Use% Mounted on
/dev/sda1             182G   42G  131G  25% /
tmpfs                 505M     0  505M   0% /lib/init/rw
udev                  500M  140K  500M   1% /dev
tmpfs                 505M     0  505M   0% /dev/shm
/dev/sdb1             230G  146G   72G  67% /mnt/sdb

So I am not running out of disk space.

When I run top, I get this output:
Tasks:  90 total,   3 running,  87 sleeping,   0 stopped,   0 zombie
Cpu(s):  7.0%us,  3.0%sy,  0.0%ni, 82.7%id,  6.6%wa,  0.3%hi,  0.3%si,
0.0%st
Mem:   1032748k total,  1013748k used,    19000k free,   242992k buffers
Swap:  2017272k total,     1040k used,  2016232k free,   473584k cached

So I am not running a process that is taking over the CPU.

How should I go about diagnosing this problem?

Thanks!

Mark