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Sudden onset palpitations, weakness, giddiness especially in morning can occur due to precipitation of severe anxiety
or panic attack
. The attacks usually last for about 15-20 minutes. Drinking water slowly help in relaxation and it aborted the attack.
Other possibility is hypotension
. Sudden standing after lying for some time result in syncope. I would advise you to consult a Psychiatrist
for expert opinion and evaluation of anxiety.