iPhone turns on but lags, turns itself off, and won't stop searching.

My problems started a couple weeks ago when my phone started turning itself off and was in a continuous Apple logo loop. The Apple logo would appear, stay on the screen for a while, and then the screen would turn into stripe, or just blue and black, basically anything other than it was supposed to be. To fix this, I began holding the lock button down while the Apple logo was up and it would turn off, then I was able to turn it back on.

Eventually, this got worse and I restored my phone.

After restoring, I went about a day with no problems, then it started restarting itself again. But it was very mild and I wasn't very frustrated with it at that point.

Now when I turn my phone on, I get the Apple logo, sometimes for a long or short time, and then the screen turns black. It either vibrates to say it's on while the screen is still black, or it shows the Apple logo again. When the screen turns black, after a while my lock screen will come on. From there it either stays on or restarts itself again. If it stays on, I'm lucky if I can unlock it. If I get that lucky, everything is extremely laggy. I'll tap on an app and it won't pop up for another 40-60 seconds. Also, it won't stop saying it's "Searching..." I've taking out the SIM card and put it back in, nothing.

I have opened it, sometimes you can tell the screen is on from the inside, but it's just black on the outside.

Should I get a new phone or is there anyway I can fix this? What's wrong with it?

-Selena