Issues while starting the car

My 98 Toyota Camry has been having few issues while starting for past few days. When I turn the key, sometimes it just doesnt start. The radio will turn on, but AC and engine remains off. If I try it again immediately, it might start. Sometimes I have to wait for 5 mins before trying again.

I went to one mechanic and he said there is little he can do since the car was starting at that time. Since this doesnt happen all the time ......any idea?