Many of these reactions are explainable, like the pins and needles, electric feeling when startled/ shocked.. it’s a adrenaline reaction and linked to the flight or fight response. I also get this.
the belly button thing, first person I heard say about this was my little brother when he was like 6/7.. he randomly said when he puts his finger in his belly button he gets a weird funny tingly feeling in his privates😅, we all looked at him like it was strange but told him “well then don’t put your finger in there then 😂”.
some mentioned sneezing or coughing when cleaning ears with ear buds.. When I clean my right eat there is a certain point that if I touch it I get a tickling feeling in my throat, if I rub it to clean I choke and have a coughing fit.. only happens with my right ear though.
as a child my “party trick” would be to twist my wrists and ankles all the way round.. I initially thought it was normal, my elbows and knees also over extend. When I got older I found out I have a certain Hyper-mobile disorder or collagen disorder which caused it and now has caused a plethora of serious health issues😬🤦🏽♀️.
I also have the hives with water/sweat thing, but I also have Mast cell activation syndrome to blame.
there are many I cannot think of right now.