Always good to have a reason I have also had this happen when my folate was low , it may be worth you getting it checked I had self inject my B12 every 4 weeks for the last 20+ (cannot really remember how long accurately), and 2 months ago got a similar 'electric shock tingling' all over my body - head, face, arms, hands, legs, feet etc within a couple of minutes of injecting, which lasted about 3 seconds or so
Immune System Support and Anti-Inflammatory Response Animal studies indicate that BPC-157 has potent antioxidative properties, which could reduce the inflammatory response in the brain, liver, lung, and other tissues
Injectable BPC-157 at standard dosages of 0.25 mg to 0.5 mg daily appears well-tolerated in community reports, though individual responses vary
Take photos every few days under consistent lighting
So thats the background biology
It is involved in the production of brain chemicals related to mood regulation