My Iphone wont turn on...this happened a few months ago with an update and it crashed my phone

I have an I Phone 4 and it was working this morning went to use this afternoon the phone is dead. I tried charging it wont turn on at all. I had this happen a few months ago when my phone automatically updated and it crashed the phone. Apple had me do a restore to the phone. I did copy everything to ICloud but is it a software or hardware problem and why wont it boot up. or how do I get it to boot up. Its saying in ICloud its offline.