Intermittent problem starting. Turn the key and the engine doesn't turnover.

No sound from engine... engine not turning over... Suspect failing starter!!

We have a 2001 saffari van which which sometimes out of the blues just not won't start. we thought it had to be plugged in but it also happens in warm weather. Gas sensor and lines has been changed. It won't start go out next day will start or it sometimes we can be 10 minutes later and it will start. The vehicle may run ok for a couple of weeks then it starts. Last week it would not start on 3 ocaisions. Please help. Thought about the starter but mechanic says he doesn't want to start pulling out wires for a bad connection. Mollyford