I have been having this vibrating feeling in upper back while laying down and sitting and when I wake up. What could this be?

Uncertain. It's uncertain whether you are describing your sensation of palpitations (of the heart), muscle fasciculations (involuntary contractions) or something else.
Many things. Problems like these can only be correctly handled by your doctor in person. He/she needs to listen to you, perform an examination and possibly run labs or other tests. That's the only way he/she can find out what's going on and what to do about it.