How can I fix my opel corsa lite 2002 not starting?

Hey Guys

This morning I got into my car and when I wanted to start it it didnt want to start at all. The starter didn't even turn at all.

My battery is fine. I tested it.

This has been happening quite a few times now.

Where i'd be driving with it in the morning and it is fine, then i'd quickly go into the shop and when I come out? Wont start again.

I've removed and fastened the battery terminals about 3 times. They seem pretty tight. I also jacked up the car to check the starter and it seems that its no loose terminal giving me the problem.

This tends to happen about once every 2 months. Usually at the worst time, since it would be working perfectly fine and then the next time I try to start it?

Nothing at all.

Anybody come across this problem or a solution to it?

I cant really take it in this week and I have an exam in 2 days which I have to attend, therefore I cannot really send it in right now