It could be MS. Does your arm hurt at all? I know that when I have bad muscle spasms in my arms I will wake up like that and with nail marks on my palms.

It could also be a type of arthritis. Morning stiffness is typical with arthritis. Try some ice or heat, which ever makes you feel better or try SalonPas. They work great for that type of pain.

It could also be something totally different. I would put a call in to your PCP and take it from there as at this point, you don't know if it is MS or not. Let us know how you are doing and what the dr. says.