When my third eye chakra opens exactly between and a little over my eyebrows I feel a deep tingling or sometimes a deep pressure that I have to press with my thumb to get relief. Other chakras are my heart where I feel a little pressure. When the throat chakra opens I get a tingling and hear a physical sound coming from the center inside of my neck that goes together with the tingling. That one is the most interesting one. It’s rather dramatic and really physical.
I’ve never had any sensations with the first chakra opening, and that’s probably because it’s alway open and the main one I function from.