The first kundalini at least in my experience is an orgastic experience... but the word orgastic seems but a shade of the sensation. So, yes, it has definitely a sexual feel, and sexual rituals can start it when that person is internally ready for it. It doesn't have to be tantric though.

I agree with Crow that self-love is the onset of everything, and having sex is a physical form of love and self-love. Since the snake rises at the root, the chakra of the physical reality and groundedness for me, and rises first to the sacral chakra this suffices to explain the initial sexual feeling of Kundalini. But that is but the onset. As the Kundalini rises more and more, cleans more and more of the lower chakras out, the more it loses its sexual orgastic nature, and loses some of its burning ferocity. By the time it reaches the heart, it remains as overwhelming, but as if all the world is hugging you, and you can lift the world in your arms and hug it back (and that image doesn't do it justice... for me it's more like the smell of fresh baked bread, the world as a big pile of down feathers, weeping tears and seeping blood from the wounds by thorns for the grail, ). Can't say how it feels beyond that, because that is as far as my Kundalini work has gone since my first experience nine years ago - the heart.

I have a question--& it's open for discussion. Which one is the highest? the 7th(Sahasrara) Chakra or the 4th(Anhat/Heart) Chakra? In the teachings of Kundalini, it is said that when Kundalini arise, it rises until the 7th Chakra but then it goes to & rests at the 4th Chakra.

Here's a thought of mine. Say, I'm a drunkard & trying to quit my drinking habit. Though I want to quit in my mind, but my heart cannot. No matter how hard I tried, I can discard my drinking habit only after my heart is in accord with my mind.
Isn't it the same with Kundalini? You must raise it to the 7th Chakra, but then it must be resided in the 4th Chakra.
    Another thought: If we go to outer space, there's no up, down, east, south, west, north in there. The only thing that exist is what in Arabic term called "Radius", equivalent of "Quadrant" in English--that is the direction based on the position of the person itself, like my right side, or my left side, etc. Because there's no directions, centre becomes important, for directions are determined according to a 'centre'.  
    Based on the above example, to me, Kundalini is as the same as consciousness. The consciousness that we're in is the reality where we live. The reality of a fly is different from human reality. A fly have thousands of eyes; compare that to the way we see things with just 2 eyes. And how about a bat? Today, there is USG(Ultra Sonography) with which the foetus inside the uterus can be seen by means of sound wave. When I first learned that bats cannot see, only hear, I felt pity for them because I compared it to us, humans, if we lose our seeing ability. But after I knew about USG, may be it is us that shall be pitied of.
    So, when a chakra opens, it creates a new reality to the person. And I think the chakras are not 'linear', like it must be opened from the lowest to the highest. I see the chakras as something like the needles of a clock. Any needle(any chakra) that turns, will consequently makes the rest of the needles(chakras) also turn. And just as the needle which determine the hour makes greater movement for the others, so with the chakras. The higher chakras, especially the 7th(Sahasrara) chakra can make greater spiritual development compared to the lower ones.
    For addition, the Sahasrara(7th) Chakra is the Chakra of Change--of creating--while the Anhat(4th) Chakra is Chakra of the Soul--Chakra of subconscious, of automotion. Anyone who ever learned how to drive a car must have known it. The will, the intention must came first, but to make it automatic, spontaneous, it must be made into a habit. When someone learns to drive, if he sees a red light, he will think of the instruction to release the gas, decelerate the gear, and press the brake, but it all still in the mind, not the heart. After he gain proficiency, all the instruction will executed without thinking, only from the heart.
When you activate your Chakra, even just by intending it, the Chakra will open. But after you stop concentrating on it, it's closing back. Let your subconscious takes over, & it will keep the Chakra stays open, just like what it does to your heartbeat.

Maclir,

Most yogic traditions consider sahasrara as the highest chakra and raising the kundalini to it as the ultimate aim.

But Sri Ramana Maharishi, the advaitic guru of 20th century says the bringing the kundalini from sahasrara down thru amrita naadi(NOT sukshmana naadi) to the heart centre. the path of the kundalini is an arc ending in  anahat and not a straight line in sahasrara.  Thats something unique that I have heart about kundalini.