I don't mean to downplay your fears at all, but I feel like by constantly rolling your wrist and checking, you could be feeding into an anxiety that is causing you Somatic symptoms. And the more you feed into that anxiety by checking, the more your brain says, "Hey, he's checking this all the time so this must be important", thus somatic symptoms and hyper-awareness of your body.
"The earliest symptoms of ALS are typically obvious weakness and/or muscle atrophy. Other presenting symptoms include trouble swallowing, cramping, or stiffness of affected muscles; muscle weakness affecting an arm or a leg; and/or slurred and nasal speech".
Now when they talk about weakness, they talk about clinical weakness. Too weak to stand, too weak to lift a glass of water, or too weak to lift your child. That kinda thing. Believe me, if you had the onset of this, you wouldn't be asking us. You'd be pounding on your doctors door. Also if you don't have any slurred speech or nasally speech, then I'd say that you're really in the clear. Try for a full day, not rolling your wrist and just going about your day as if nothing is going on. Your thoughts create your reality, so tell yourself "I am fine and am of perfect health" and repeat this affirmation throughout the day. Chances are if you get through that day without any symptoms, you are just fine. :)