First of all, keep in mind that I am unable to diagnose you because I am unable to examine you, this forum is for educational purposes.
The symptoms and story that you describe are non-specific, but are unlikely to be ALS (amyotrophic lateral sclerosis). ALS generally presents with weakness and atrophy that is rapidly progressive. This is also associated with fasiculations (twitches in the muscles) in the distribution of the weakness and atrophy. Cramps are also common due to painful muscular contractions. Numbness/tingling is not typical for the presentation of ALS.
The story you describe sounds like benign fasiculation syndrome. Fasicualtions can occur for many reasons and are not a marker for ALS. Fasicualtions can occur in normal people, with excessive exercise, after a viral infection and with electrolyte imbalances. Benign fasiculation syndrome has wide spread fasiculations (all over the body) and is not associated with weakness or atrophy. It is reassuring that your MRI is normal (which makes multiple sclerosis much less likely). It is very hard for anyone to have a loved one diagnosed with ALS and it is natural to worry about developing these symptoms yourself. Given your symptoms I suspect benign fasicualtion syndrome, but I would suggest that you get an EMG (nerve muscle test). This is the test that is most often abnormal in ALS. I think your EMG will likely be normal and will give you some reassurance or help you with addressing any abnormalities.
I hope this has been helpful.
My boyfriend is a very healthy 39 year old. When we first started dating I noticed that his left eyelid was a little
sounds more like bfs - benign fasciculation syndrome (i can never spell this correctly). you can look this up. i think you would know if you had weakness. just because your cousin has it does not mean you do. if it continues, you could always discuss an emg with your doctor. have you had a physical exam by a neurologist?