1995 Nissan Maxima Nissan Maxima starting problem

I have nissan maxima 1995 and I am having problem with starting the car. During the winter I had this problem and I changed the battery. After few day the problem came back. Sometimes I turn the key but nothing happens, no cranking sound. After few tries it does work. If I don't start the car for few days the battery drains out, and in such case I had to jump start the car. I showed it to one technician who said alternator and starter is good, but the problem could be in the ingition switch. He put a push starter button which I have press and hold down after turing the key on - but the car doesn't start right away - sometimes I have to push and hold it down for several seconds. In this process sometimes the battery drains-out and it doesn't start anymore without jump start. I showed it to someone else but no one can confirm and point out the exact problem. Could you please give me an idea what could be the problem?