After Booting up issue

Hi! A couple of weeks ago, I powered on my Mac. A screen appeared with 3 icons: drive icon i.e. “Macintosh HD”, underneath “an upward looking Arrow”, and “WiFi signal” with the option “Choose Network”. When I clicked the drive icon, it asked for the password, which I fed but was not accepted despite repeated tries. Finally clicked the “Forgot Password” option and chose a new password. I did the hard-restart and this time tried to punched in new password - instead of showing password, it started splaying weird symbols - also, did not accept the password.

Had a long call-session with Apple and was asked to punch various keys, including resetting of NVRAM, but nothing happened. I then myself reset SMC which worked. As for weird symbols, I fixed it through Accessibility option. Mac worked fine for couple of weeks but today when I powered up, the same screen appeared with same issue. I did NVRAM reset - nothing happened. Then did SMC reset and this time it did not work.

MacBook Air IssueAny suggestion please!