Have you ever spent some time on your cell phone and then felt this "deep warmth" in your head? I've felt the same warmth after having gone through a "full body scanner".

I've mentioned this to a coworker before and he laughed at me. Then I heard him be on the phone for like 30 minutes and during lunch he mentioned that his head was feeling this weird warmth. I repeated my theory and asked him what are the odds of his phone usage and the warmth being unrelated. I've never seen him not use headphones when being on the phone since then.