I am a electronic technician and Java Software Programmer with 24 years, so I attempted all suggestions in here and did even many other "tricks" but NOTHING worked. I am convinced it was NOT a HARDWARE problem. So I suspected it was a software issue, a misbehaving app? virus? OS/firmware corrupted? or something like that so..... I reset to factory reset and now all is working fine. Unfortunatedly, I lost many files but restore about 80% succesfully thanks to two things:
#1. Google acccount backup in the cloud AND #2. I setup a SAMSUNG account with SAMSUNG backup and I restore many files but not all of them. I should had added my download folder to the Google Drive auto backup but I never set that up! In any case the phone works perfectly fine now, which confirms beyond any doubt that it was NOT a hardware problem but a SOFTWARE issue.