JimR,
hahaha! Better take the bus. Might be less stressful!
Yes, my GP recommended taking magnesium supplements since magnesium is known to relax the body and the muscles. However, as you already said, I don't think it is very effective unless you have a proven magnesium deficiency. Another mineral you should have enough of in your body is potassium. Eat 1-2 bananas a day and you are fine.
Have you already conducted a 24 hour holter? In my opinion this is quite important to determine 1.) how many ectopic heart beats you have in total and 2.) whether there is a higher cardiac arrhythmia (which we of course don't think you have).