You didn't mention what you do for work or play, anything repetitive? As a telephone operator, many years ago, I damaged a small nerve in my elbow from repetitive movements in answering the telephone all day, 40 hours a week. The funny thing was, while the nerve damage was in the elbow the tingling sensation was felt in my little finger! (and it was constant) A trip to the Dr. confirmed that I needed to ease up and change the way I was answering the telephone.
Regardless of whether anything similar is true for you, a good chiropractor may have the answer / solution. Acupuncture may also be a source of relief. In any case, it is highly unlikely that it is anything deadly, or debilitating.
Another source of nerve damage is being reported in connection with things like the flu shot, and other vaccinations wherein weakened or killed viruses are injected to enhance immunity. If you have had any of those in the past few weeks or months, that could be the source. In this case too, the nerve damage is temporary, and will eventually pass.
No thoughts as to why it occurs when you are reading or when excited.