odd sensation in hand and foot

I have noticed for the past month or so and odd almost tremor type sensation in my left hand and foot...on several occasions my thumb has involuntarily "jumped" only for about 30 minutes and only a few times...I mostly noticed it when I was at rest but now feel the sensation (can see any movement) in my foot all the time.  Yesterday I was standing at a counter top and was standing with my left foot bent over with the sole of my foot facing my right leg and my whole leg begin to tremor...when I put my foot straight on the ground my leg stopped.  My mother has MG and my Aunt died with something much like ALS - I've forgotten the name of it but she had many of the same symptons such has slurred speech, difficulty in swallowing, had to be put on a feeding tube...Thoughts?