My z750a won't turn on!

I have this phone and must say it has totally pissed me off at this point so I understand everyone's frustration. My phone had many of the problems posted on this sit but here is the solution to your specific issue, which I just had to fix on my phone yesterday.
First, the people at the phone stores will tell you it is the battery - IT IS NOT USUALLY THE BATTERY! The OS (operating system) for the phone is the worst I have ever seen.
The FIX - Go to the Sony Website (http://www.sonyericsson.com/cws/support/softwaredownloads/z750a?lc=en&cc=us) here you will the update to your phone software. Download the software and follow the instructions. Yes, it will work even though you seem to have no display.
Warning---- This will erase all the phone memory and reset it to original factory setting. You will lose everything not back up on a memory chip or the SIM card. Also, you will need to use a phone to usb cable that you may have to purchase (10 dollars or so). To get the phone working again it may be worth it. I back up my phone to my computer so that I maintain picture and such that I do not want to lose.

In general I back up my phone frequently because the OS becomes unstable and crashes the phone. I do an extraordinary amount of texting and if I receive a text and send a text at the same time the phone just gives up sometimes and shuts off. And, this phone is the KING of shutting down for no reason whatsoever. I have had so many issues with the operating system that I will not get another Sony phone. Back to Nokia for me. Hope this can save some people the time and aggravation I have had with it.

I encountered the same problem with my z750a phone. It is not a battery problem. it happened right away (3 days after i bought my new phone from the at&t store). i took it back to the store and they told me to call the manufacturer. basically, i got the run-around. what i figured out is, if you hold button that turns it on for about 3 sec, it'll start to virate. it wont turn on just yet. do it again, and the screen will light up. do it a third (or sometimes 4th ) time and the phone will turn back on. i have to do this EVERY single time my phone randomly shuts off on me (in the middle of a conversation usually). hope this helps.

Could be one of two things. The battery is so used up that it will no longer charge, or the charger may be bad. If you haven't already, try and use a car charger. If that is not an alternative, take it to an ATT dealer and ask them to evaluate it. There usually isn't a charge for them to check it.They will use one of their plugs momentarily to see if the phone will stay on.