Dear @Shrinath, Kundalini energy is a very powerful energy. In the process of rising upwards from your Basic Chakra, it cleanse and activates your other Chakras – one by one. The peaceful feeling is because you were restless and your sub-consciousness asked for it and the sensation in third eye is probably the effect of getting into meditative trance.
If you visualize a scenario, when you switch on the main-switch of a non-operative manufacturing unit, and the production line suddenly starts working. Its the same situation here. Your sensations are because energies at different levels have had started playing causing sensation. Nothing to worry…..please keep it up.