[Eljaro]

well, problem solved!
On my last outing with "no start " situation included I accidentally hit with my elbow the battery disconnect switch while pushing the car and disconnected the battery. Uppon connecting it back again the starter came on inmediately.
I checked the switch which was ok, but the key had a worn plastic stem and didn't push the contacts firm enough together.
Since the contacts with the bad key had between 1.5 Ohms and 8 Ohms cold , they probably got hot while driving ( I also noticed the charging gage erratic behaviour sometimes), the resistance value got up and not enough amps would reach the starter. That was it.
I got a new key with a metalic stem and the resistance of the switch is now 0.4 Ohms.