starting problem

[rollinbeaver]

Yes, it very well maybe the CMOS battery. Hardware problem, not software.    Probably a CR2032 

I'm no longer wondering. Yes, that sounds most likely.

And those batteries ain't tiny: a CR2032 is a "coin cell" of eponymous dimensions, at least a centimeter in diameter.

If you have small good tiny tools and a little experience with opening up a laptop you should be fine.  Possibly it is just small torx or phillips scredrivers and a tweezer.  If not, starting up with the power supply would work also.

I could'nt find a disassembly guide for your model, but generally, there's quite some screws (likely Philips) in the bottom part holding fast the keyboard and the surrounding bezel and body shell.
Next, you should put something like a guitar plectrum or credit card corner into the seam between the body shell  top and bottom and gently apply leverage to successively separate plastic latches around the seam.
Careful with the connecting cables of keyboard and touchpad.
Then, if you're lucky, maybe you already see the battery in a holder on the mainboard somewhere. It should IIRC have slightly more than 3V to suffice.

[benton]

Thank you rollinbeaver for advise, I will open the body shell next week and will come back with a report.

Nice weekend
benton