Funny you should ask this question, I've been meaning to ask a similar one for a while now.
For years now, off and on, I get an awful feeling in my chest if I am woken up suddenly, esp. if I've just drifted off to sleep. It feels like my heart is beating a million beats per second. I once wore a halter monitor to check for any heart irregularities because of it, but nothing registered. It must be tremors or spasms (if those are different things). I always check my heart rate when it happens and its normal.
Once in a while I do feel it in my arms like you mentioned, but I'm ususally so distracted by my chest feeling so weird I don't pay attention to the rest of me. Does that sound anything like what is happening with you?
Great question - cause I get them too - they seem to me to be inner trembling. I hate them - they make me feel anxious. I get them more when I lay down for a nap in the afternoon. I wake up in a semi panic, as I do believe that it is the inner trembling that has woken me up.
I do not get them very often when I go to bed at night, unless I get up for some reason after I have slept for awhile, and then when I go back to bed, and lay there - I get the sensation.
Interesting to see that seveal other get the same thing.
Have a nice day