Xperia :: My X8 Keeps Rebooting

i was wondering if anyone in this thread could help me with my phone. Its a xperia 8 and i only bought it 2-3 months ago but its haveing some problems. for about a month now its been making the sd card removal noise for no reason that i can tell and the battery has been running out pretty quickly (although this might because its searching for signal as my work doesnt have the best reception) with the battery being full when i start work and empty or next to when i grab it from my locker even 3 hours later. this wasnt so bad cause i just turn it off when im at work untill recently when it started going really slowly taking minutes to open simple apps. and about a week ago it stopped turning on propperly altogether. when i turn it on it starts up as usual and as soon as it gets to the main screen the screen goes black and it tries to start back up again 30 secs or so later.i have found out that it will actually stay turned on when i turn it on when the power is connected to it but this makes it im-mobile (kinda defies the purpose). un the power cord isnt sitting right in it as it keeps starting and stopping chargeing (although its been doing this since i bought it, wasnt such a problem as it gets a full charge by the mourning anyway) which stops be being able to keep it turned on long enough to do a system reset or anything that i can think off.