heaviness in both arms and shoulders

I have had several episodes of temporary weakness
Weakness
or heaviness in both arms.  The episode doesn't last very long - perhaps a minute or so.  It's happened three times in the past 3 weeks and I remember it happening a couple of other times more than a year ago.  When these episodes ocurred I hadn't been doing any physical exertion.  The weakness
and heaviness is in both arms from the shoulders
and is fairly overwhelming when it happens.  It's as if I can't lift my arms or use them.  There isn't really any pain or other symptoms.  Does anyone know whether these symptoms are signifcant - should I see a doctor?  Do you know what causes this to happen?