Recently I have felt these sudden attacks of extreme peace such as I have never experienced. A feeling so heavenly that it's unfamiliar. All I can say is that the only way to describe it is 'heavenly'. That's because I know not any other way to describe it. It comes for a period of about five to ten seconds then disappears completely. It leaves me wanting more, as scaringly sweet as it is. It must be something to be a being of complete light.
I have experienced this recently too. Try this - get into a meditative (or even just sleepy) state, and send absolute, unconditional love to the entire earth, the moon, the ships above the earth - everywhere. Picture an amazing light show of love just filling everyone and everything on Earth. That's how you'll get that feeling again. When you imagine this, and feel the love you send, someone somewhere sends love back to you, and what you described is exactly what that feels like.