cntexas,
i get exactly that i have catnap in the afternoon and wake up feeling nervous and by heart beats so fast i think that it might be where its a bit of a shock to us when we wake up. Everything is a shock to me at the moment i am so sensitive to everything, if someone calls me and they are out of breath or something i automatically think that they are in danger and i get a shock feeling, like i am exited or something ( its a bit like that feeling when you are exuted to go on holiday or something)maybe it is adreneline?