I hear a click but the engine does not crank?

Hi

When I start the van every morning - I hear a click but the engine does not crank. After 2 or 3 clicks, it starts alright. All other electrical systems seem to be working - I can feel the fan come on, radio and dashboard lights are all ok.

After the early morning starting issue, the next time during the day, it takes one click, but starts on the second one.

Please help me in diagnosing what the problem could be.

Thanks
Kal