On Several Occasions...usually At Night...I Have A Limpness In My

On several occasions...usually at night...I have a limpness in my left arm, perspiration on my head and a general feeling of malaise. I cannot stay lying down and must sit up. Each time I go to lye down the discomfort returns and I must sit up. I most recently found that drinking an electrolyte drink (Gatorade or coconut water) seems to make me feel much better. I have had problems with dehydration in the past.