Device is continue in boot mode and does not start.

Try booting while the device is charging. If the problem disappears, that means your battery is faulty. If the problem continues, there any many places to look at. First of all, there might be a problem with software, (if your tried rooting in the past). Other things might be the cpu or even the controller chip related to the sim. I recommend, trying booting the phone while plugged in, at first, and then search on youtube or google for posible problems. If you can’t fix it, have a professional take a look!