One night, a couple of months ago, as I readied myself to sleep, I felt a strange tingling sensation moving all through my body. It was certainly not cramps. But a joyful sensation that continued for a couple of minutes. I sense that it does not have only a physical explanation.
Please shed some light on what it could mean.
It would be easier for me to answer your question if I knew whether or not you are a meditator/sincere spiritual seeker.
But if you are either, the explanation would be that this sensation is the awakening and moving about of the prana (life-force or conscious cosmic energy) inside your astral or energy body — being caused by whatever you are doing to awaken yourself spiritually.
It is a very good thing, and this is why you would sense it as being joyful.
And you are right that it goes beyond being a simple physical sensation. This sort of feeling is not at all unusual for sincere spiritual seekers to experience.