Hello, Your symptoms of intermittent cold sensation, mild sweating and tingling or pin-prick sensations in different parts of the body need further evaluation. Possible causes include vitamin B12 deficiency, thyroid dysfunction, blood sugar fluctuations, electrolyte imbalance, peripheral nerve irritation and sometimes anxiety-related autonomic symptoms. Is there any history of smoking or any other substance abuse or alcohol consumption? I would recommend the following initial investigations: CBC Serum vitamin B12 Serum vitamin D3 Serum electrolytes, calcium and magnesium Kidney and liver function tests Since you also have neck and back pain associated with prolonged bike travel, a clinical neurological examination is advisable. Your normal ECG and 2D echo are reassuring, but if you experience chest pain, fainting, significant breathlessness or profuse sweating, please seek immediate medical attention. Please consult a neuro physician for a detailed physical and neurological examination.