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The camera might be (from the erratic sound of the symptoms of failure that you describe) a case of electronics failure. However... there are some things to try on it:
Try removing the batteries, and leaving the camera on a (dry, non-humid, non-dusty) shelf for overnight. Then put the batteries back in and try the camera again.
Then try cleaning the terminals in the battery compartment, after removing the batteries, first by rubbing off with a fresh pencil eraser, then by wiping the terminals off with cotton swabs moistened in rubbing alcohol, then letting them dry off for 5+ minutes with the battery compartment door open, then try turning the camera On again.
How long has the battery or batteries in the camera been in-use? If over a year, then you might possibly have a battery/batteries that are getting weak. Rechargeable batteries do get weaker with time, and eventually fail to deliver enough power to start up a device like a digital camera; they then need replacing. The replacement battery needs to be charged up for 6+ hours before its first use, owing to its having been on a shelf for a considerable time.
How old is the camera? (even a rough estimate would do).
Has the camera been dropped or otherwise subjected to mechanical shock(s) in its lifetime?
Has the camera been operated in or subjected to, temperatures below 32 degrees F (freezing point) or above about 100 degrees F ?
Has it ever been subjected to a humidity higher than 85 % or gotten wet ?
Has the camera been operated in a gritty or sandy environment, such as a beach, a seaside, a construction site, or the like?
It is good to hear that you yourself have taken good care of the camera.
But something is wrong with it - and hopefully it may prove to be temporary and the resets and considerations I suggested may help.
The symptoms - if it proves to be a major, not-temporary problem - are those of a circuitry failure. But that could come of defective/aging batteries or poor power-supply to its circuitry, too.
Thanks for the response. Let me know how it goes, please.