My N95 has started to have a boot up problem

My N95 has started to have a boot up problem, at 1st I thought it was the battery as it wouldnt hold a charge or work unless it was on charge, when its on charge the charging bars move like its taking the charge but once you unplug it it just blanks out, I have bought a new battery but still same probs, I have been able to switch it on twice the nokia sign comes up and a minute or so later it goes away if I press any button it lights up but wont boot into phone.