Engine not cranking over starter, ignition switch and battery and they all work

I purchased a used 1996 infiniti i30 about a month ago, and sometimes when I try to start it, it wont start. The transmission and engine are great, and the car runs excellent. I took it to a friend who is a mechanic and he could not find the problem. He test the starter, ignition switch, and battery, and they all work.

Here is the problem:

I put the key in, and when I turn it, it wont even make a noise. All the lights on the dashboard will come on, but that's it. This only happens sometimes, and the car works perfectly all the other times. It worked 10 times in a row the past few days when I tried to unlock and lock the doors with the key (manually) because I thought it was the securtity system. It still might be the security system, but I tried to start it by using that technique, and it didnt start. If it does not start the first time, It takes about a minute of continuously turning the key to get it to start. It worked twice today when I put it in neutral and then tried to start it, and sometimes it works when I turn the wheel a little and then try to start it.

Sorry this is long, I just tried to give as much information as I could to make it easier (or more difficult) to answer.

Any help would be greatly appreciated.

Thanks!