issues regarding my arms

For the past year+ I randomly experienced episodes with my arms.  It's hard to explain, but my arms become VERY heavy and very weak.  I can hardly move them.  I experience a discomfort also.  The episode lasts less than 30 seconds and is then gone.  I am weak in my arms for many more minutes.  When this first began, I experienced it maybe twice a year, but lately (the last 2 weeks) it has happened 4 times.  I don't know if this is neurological or not, but this is where I am starting my search.  I mentioned it to my doctor and she said she has never heard of it, but it may be neurological.  My mother, who is 81 yrs old, has mentioned to me that she has experienced this also, but I doubt it is the same thing.  I am so very concerned, I just want some kind of answers.