1997 Chevy Lumina will not always start

I am not sure of the engine size. However the problem started when my keyless entry no longer worked. The dealership said that shouldn't affect anything, but there has been something wrong for about 3 years now. I have always followed the manual for starting my car (no foot on the gas ect). But at nay given time, it just won't sart. I don't have my key on a keyring or anything heavy. Then I open the hood, bang on the relatively (about 2 yrs old )battery and about 2 minutes later, it wiil start. I have no idea what I am doing, but it usually always starts.
I just had an oil change and the guy said something about my "tumbler". It wouldn't start for him, and I explained to him that I had it in about 5 times for diagnostics, but no one could figure it out. I do know that when I insert the key it always makes a slight "current" noise, and electrical sound. It sounds like a connection sound, kind of a speckly sound.
I would like to resolve this because I am at my wits end. It is a one owner (me) vehicle, and I would like to pass it on to my son.