It is quite common to have this problem of arms falling asleep during sleep.
This is because you put pressure on your nerves making them numb or putting pressure on your blood vessels resulting in narrowing of blood supply.
In fact what is more important is whether you feel numbness
in day time as it may mean some deficiency like electrolyte imbalance
deficiency of VIT B12,VIT D,calcium etc.
As far as skipping the heart beat is concerned,it may be normal if you experience it occasionally but if it is happening on regular basis,then you may have to consult a cardiologist
and may get HOLTER monitoring