thanks for your wonderful advices towards mentioned reason below

there are many reasons a person can feel weak and dizzy. One of the most worrisome reason we need to rule out is an inadequate blood supply to brain. It can be because of dehydration and low salt intake especially if it occurs when standing from sitting or lying position suddenly. if the weakness and dizziness is more prominent with exertion, we need to rule out underlying heart conditions like heart block, symptomatic bradycardia. If it is a room spinning sensation and associated with nausea/vomiting, Associated with change in position of head, associated with ear problems, then it could be a problem of vestibular system. Sometimes, simple thing like anemia can give you weakness and dizziness especially with exertion. If everything comes back normal, you would want to make sure that there is no atherosclerotic blockage of the arteries supplying to brain.Hope this helps!