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Some times during sleep due to a lot of reasons obstruction of airway occur usually seen in obese
individuals, due to apnea
individual suddenly wakes from sleep and some times he feel frightened, tremors, anxiety
and weak. It is usually normal. But it may also point to some Anxiety Disorder as Panic Attack
may occur in any situation and it is a non specific anxiety. But if the thing recurs then visit a good doctor and get your ECG done to rule out any cardiac cause, if its normal then visit a psychiatrist
At present you need not to worry.