My phone won't turn on, charging icon loop

My phone won't turn on and when i connect it to the charger sometimes it shows the charging icon and then goes into a loop, and sometimes it shows the charging icon one time only and then it dies.

Also if i try to boot into download mode, it works but it stays for like 10 seconds and then reboots, so i guess maybe the power button is faulty and always pressed?

What do you think?