Thanks for the links, I've tried to auto-induce the sensation with sound or images but it doesn't seem to work for me. It appears to just be a people thing.
I know what you mean. It's good to try and explain it to others, but unless it happens to you it's a bit tough to explain the sensation. I'm glad i was able to help.
For me, it's more than just head tingling, it's a flood of utter joy and elation. It's an awesome experience when it happens. Quite where it originates from no one appears to know, and because it appears to be a good experience, no research is going into figuring out why it occurs (which is reasonable).
I used to get it a lot when I was younger, normally when people were doing me a favour I wasn't expecting or they were going out of their way to help me. I've also had it when getting my hair cut.
Throwaway account, as I have also had the crazy look.