iPhone 6s bootloop even after multiple restores to 10 and 11

As the title says, my iPhone 6s have been failing for the past 2 weeks. The first symptom was my carrier signal wasn't getting caught by the iPhone, it was stuck at searching even after some restarts.

Then I made a factory new restore to iOS 10.3.3 and everything was running well. Then after a couple of days my iPhone just got to the Apple logo (bootloop) after doing just random tasks (daily tasks) and all I could do was to restore again. Everything was fine until it did it again the bootloop. I have had to restore 3 - 4 times to get it work, but my phone is getting unusable.

I also restore to different iOS in this case 11 but problem persists.

Please help me, I don't know if it's a battery issue, or logic board but I can't find any other person having the same problem.