Hi ,I have been experiencing unsettling feelings from time to time approx two too three week intervals ,which consist of feeling very unwell , systems as follows ,nausea , dizziness , muscle palpitations , feeling very weak And occasionally short light pain in one of my arms . I had one particular bad one several weeks ago and visited hospital where they gave me an e.c.g blood tests , a chest x ray and could not find anything wrong . The strange thing is the next day I generally feel fine . I am 65 years of age and generally very fit . I have visited my doctor and at first thought perhaps his was down to overdosing on caffiene , however I had a moment over weekend and I have not had caffiene . Can you suggest plausible explanation please .