Maruti Omni E
Starting problem

For the last ten days my van is starting with low power and shaky noise in the morning and after a gap of 2 hrs standing idle. I had got my batteries inspected, changed the spark plugs and air filter. It is giving no smoky emmission but a few water drops come out of the silencer tail end in the morning. Also the old spark plugs although changed were okay with almost no carbon or oil deposits. What could be the reason