Sun acts like a kind of giant pendulum as it moves from its winter
rising position through the equinox towards its summer rising position.
At the solstices, the Sun is rising in virtually the same place
for a few days as it stands still - hence the word 'solstice', which
comes from latin 'solstitium' which means 'Sun standing still'.
As the weeks go by its rising position on the horizon changes more
rapidly, and at the equinoxes, the Sunrise position is moving along
the horizon at a rate of about half a degree per day - which is
the equivalent of about one width of the Sun each day. The effect
is that of a giant pendulum, swinging from one solstice to the other,
slowing and stopping at each solstice, and moving quickest at the
equinoxes. The above diagram is not accurate to scale, but gives
a visual impression of the phenomenon. See this
nice site for information about the solstice.