Leo;

There are a number of things that can cause this problem. I will list some in no reasonable order.

I am going to assume that you have checked the battery connections and they are clean and tight. If not do that the very first thing. If they are not clean, tight and corrosion free then you will never get it to start.

First check and make sure the starter is tight and that all the connections are clean and tight.

If that doesn't help, pull the starter and have it checked.

On a side note, you could have a weak battery and a slightly draging starter. Each in itself would not cause a problem but the 2 combined can.

Again, I would check the connections and starter tightness first, that won't cost you anything.

I will keep an eye here to see how you make out. Let us know.

Jim