Are you referring to Restless Legs Syndrome?? Not really 'shaking' but an internal (infernal!!!!) weird jangling nerve sensation that makes you feel like you HAVE to move your legs even tho it's the middle of the night; your head is 95% asleep and your legs are running a marathon?! It's the absolute worst, and here's a link to a website that I picked up somewhere about RLS, but I think has information about similar movement disorders: www.wemove.org/rls/
If it's RLS your hubby has my complete sympathy. I thought it was all in my head and have suffered from it since adolescence but never knew (still don't) know why, since I could never get an MD to diagnose it, or for that matter even acknowledge it, they would just say "Hmmmmm.." and never had any idea what I was talking about! A recently really bad episode due to a reaction to a new SSRI lasted almost 4 days and was not just at night like it usually is. My doc told me to take benadryl, which was pointless! Benadryl may as well be a tic tac for me, drs seem to think that it is the cure for everything, what's with that?? At least the doc ackowledged the RLS as a rare but possible side effect of the meds they had me on, makes me feel not so cuckoo! Good luck, hope the site can help you out.