iPhone goes to sleep without pressing button

[rogcha92286]

My iPhone 3G has recently begun going to sleep without me pressing the sleep button, and the volume also will turn itself all the way down without me pressing the volume button. If i turn the volume back up, it just automatically turns back down. Both of these problems also occur if any pressure is put on the front of the phone, if I barely squeeze the phone, it will go to sleep. When it goes to sleep, it makes the sound like it is taking a picture..it is actually taking screenshots of the phone at the time and saving it to my camera roll. This also leads to a continuous start/restart sequence once in a while. My main problem is that this only occurs for about a half hour at a time, then it runs perfectly fine, so it's hard to convince the people at the apple store that I have a serious problem. They did suggest that I restore it and start it up as a new phone, and that solved my problems for maybe a week. The guys at the apple store said they've never heard of this problem before, so if anyone on here knows what the problem may be, input would be greatly appreciated. Sorry so long, but this phone has caused me a laundry list of problems lately.