iMac many problems

Hi, I have several problems with my Mac:

- When I click on any tab in the browser, the tab turns on and off rapidly

- At any time the display suddenly goes completely black.

- When I turn on my computer, when I try to type the password, after typing 2 or 3 letters, everything gets erased, I have to restart it

- Sometimes it won't let me turn off the computer

- It also causes problems with a music application I use (Pro Tools)

Some problems are sometimes solved by relaunching the Finder, but it only lasts a moment. I usually have to restart the computer.

I have run Norton several times and it doesn't find any viruses.

Any help is greatly appreciated. I don't know what to do anymore. Thanks

iMac 2019 3.7 GHz

Mac OS 14.3.1