2011 Mercedes-Benz S550 Questions

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I have a 2011 S550. I know for sure it sat for weeks without use prior to buying it and had "hard starting" reported. I have a recurring "dead battery" like failure where the car won't start. Dealer has been good, but baffled. The main battery, starter, alternator, regulator, and several modules have been changed.

When the dealer gives it back with a good charge, its weeks before it has the issue, then it fails to start 3-4 times a week. Jump it, drive it, starts for a few times, then fails again.

This past time, the car was dead. Turn the key fob, no dash board, and very few clicks. When the roadside tech connected the portable jump cables, the car fired right up like there was no battery issue at all.

No one knows what to do.

Any ideas? Anyone know if the battery control module might cause this? Other component that on command to start could be shorting the battery?

Should I be aware of major flaws, recalls ? What is the ideal mileage I should be looking for?
When on a highway drive lasting more than 1 hour, my heat and A/C system seems to shut down. The blowers won't work and adjusting the temp. has no effect. Must turn off car, let it sit for a while and restart it. The systems then work, at least for a while. My dealer has not been able to find the problem. Diagnostic tests come up clean. This happens in both heating and cooling seasons. My car now in shop for last 7 days and dealer is still stumped. I told them to keep car until they can find, and fix, the problem.
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