I said what it was just above. Apsidal precession is a procession of the direction of the major semi-axis [of an elliptical orbit]. There is a nice animation of it at the top of the wiki page on it.
Your understanding is mistaken. A circular orbit has no major semi-axis and does not exhibit apsidal precession at all.If I was to try and explain it simply as I understand it, imagine a small ball on your kitchen bench representing the sun. Now place a hula hoop over this with the sun in the centre. Pick up one side of the hula hoop. This presents a change in the Earth's orbital path relative to the sun. As you lift the hula hoop the distance from Earth to the sun increases, this creates the cooling phase and as you drop the hula hoop the distance decreases and so this is the warming phase.
If you pick up one side of the hoop (without lowering the other side), the sun is no longer in the plane of the hoop. This is a violation of the most basic physics: F=MA, Newton's second law. 'A' (acceleration) points to the centre of the hoop, but 'F' (gravitational force) points a different direction, towards the sun. This cannot be. Yes, if Earth could do this, it would be further away on average the more the hoop was lifted, but this cannot happen.
The hoop can be tilted differently, but the sun would remain at the centre and the change would have no effect on orbital distance. Such a tilt is called orbital inclination, and precession of the axis of this tilt (not the amount of tilt itself) is called nodal precession, and has a very long period which I cannot find, but possibly longer than the life expectancy of the planet.
A change to the major semi-axis of an elliptical orbit should have no effect other than which constellations are in the night sky when the Earth is furthest from the sun. The eccentricity (the difference between the the nearest and furthest distance) does cycle, and seems to be the dominant driver of recent ice ages. A circular orbit has zero eccentricity. Venus has the most circular orbit of the planets, or Triton does if you consider all the moons.