Waking up with slight numbness in my left arm and hand during the middle of the night. should i just go back to sleep or monitor it?

Position: Do you sleep on the side where you have this numbness. At times if you lay in one position the entire night, you may feel this numbness in your arm and once the arm starts recovering there's tingling as well. How long does it last? does it occur each night, sometimes during the day? any other symptoms?. Change positions and see what happens.

Did you fall asleep?: The symptoms you're describing sound like you may have fallen asleep on your arm This can cause temporary numbness and tingling. If these are ongoing symptoms you should be evaluated for more serious causes. however if you're young and healthy and the numbness goes away, most likely this is nothing to worry about