iPad not turning on

During the last week my iPad (3rd generation) has been very unresponsive and on a few occasions has frozen and then I have had to restart it. The same happened last night but this time time and power on the bar at the top of the screen was flashing. I tried to restart it and when the apple logo was on the screen when starting up again it turned off. The same has happened when I have started to switch it on since. This afternoon I then tried to sync it with iTunes and restore it but my laptop does not recogonise it. Does anyone have any suggestions of what else I could do. Thanks