Have you tried cleaning the earth lead at the front of the car (O/S chassis) Amar? I had all manner of problems similar to yours, lazy starter motor, self opening sunroof and windows ect. That was caused by one pesky corroded earth lead, since cleaning it at both ends all the electrical problems on the car have vanished. I cheated and added a second lead whilst I was in fixing mode
To complicate matters my car is dual fuel LPG/petrol. The installers had run the LPG supply pipes very close to the plastic petrol pipe in the engine bay and over tightened one clamp. Result? slightly crushed petrol pipe, and somewhat restricted petrol supply to engine.
Hope this helps.
Paul.