You most likely have a battery issue.
If the battery is original, replace it, do not even try to test it.
I have seen bad cells or internal connections in batteries that do exactly what you indicate. Might even be a loose or bad connection to the fuse box on top of the battery. The small wire is probably loose and may be moved when jump starting the car?
They may test good once the car has been started and the battery is warmed up, but once the car sits, it will not start.
Buy yourself a cheap Voltmeter, probably under $20, check the battery Voltage when the car will not start. 12.6 Volts is a fully charged battery. Anything below 12.0 Volts is bad, battery is 75% discharged or has other problems at 12.0 Volts or lower.
Charging the Voltage should be between 13.5-14.5 Volts.
Pretty simple?