I slept funny last night and now my arm feels numb and like dead. Can I shake it off?

How numb, how long? In the case of "one time things", ie an event which has never before happened to you but does not immediately seem serious can be monitored (by you). Things to take into account: how long is this lasting, are symptoms progressing, is pain developing, does blood flow (denoted by color and temperature) seem to be adequate, are symptoms spreading to other body parts? Care but be aware!