fujitsu laptop

my laptop(a fujitsu laptop) restarts when it is charged. when not plugged in it does not restart in any way. When its plugged in it takes a few minutes or hours (it depends) for it to restart the laptop, it also takes a while to load in once logged in(though booting time is faster), usually...

I'm having a big problem about this laptop. My laptop is a fujitsu and it's turning off by itself but i already brought it to a technician but he still did not fix it. I'm thinking right now what is really the problem to this laptop. I wish i found an answer to this forum.