Acer N50 going crazy

Hi,

I bought an second hand Acer N50 from ebay.

After 1week using it, it started resetting itself even when it was switched off. This was being done continously until the battery is off.
Then I charged it to full and it was working ok. However after I used it for 10 minutes it restarted automatically.
Some other things that are happening is that when I try to switch it on it is not switching on. The strange thing is that after some time the PDA then switches on automatically and I can use it.
Today I also opened it so I could find some loose connections but all in vain. After I opened it,it was switching on but when Windows starts the screen turns off.
Right now it is working ok but I do not think it will do so for much time.
I do not know from where is the problem, whether it is a hardware or software problem.
I was thinking of changing the firmware but I cannot find somewhere from where to download it.

I know it is a strange problem but I will be veryhappy if someone can help me.

Thanks