Smartphone lives its own life?

Question

Android

One of my classmates has a smartphone that lives its own life. He himself launches various programs. We ran several antiviruses and even started in safe mode, but everything is clear.
There are no viruses, then what's the matter? Why does a smartphone do what it wants?

Answer 1

Sequence of actions:
1. Turn off the Internet for a couple of hours - if everything has passed, then the problem is software, the hardware is 100% working, go to the 2nd step. If not, then go to step 2 anyway.
2. Reboot into Safe Mode, see if the problem is still there. If yes, go to step 4.
3. Remove hidden apps and unnecessary/obscure/unnecessary apps via Settings > Apps. The main thing is not to accidentally delete system applications. Everything went perfectly. No - go ahead.
4. Make a hard reset by backing up ONLY contacts, calendar, text files, photos, videos, documents, 100% trusted applications. It's gone great. No - reset without saving any applications. Again did not help - further.
5. Flash your device with factory firmware. This will definitely help, but if not...
6. Flash your device with LineageOS or something based on it.