First of all let me thank t@endsormeans and @pali
Both were great in helping me and we agreed that there is realy a hardware problem
First Pali told me do stop bme on terminal and see what hapened
My N900 would shut down few minutes later
Second step was and i quote
"First enable R&D mode via flasher-3.5 --enable-rd-mode and then set
> those R&D flags which disables watchdogs and lifeguard via flasher-3.5
> --set-rd-flags=no-omap-wd,no-ext-wd,no-lifeguard-reset"
Simple but efective
Problem is hardware and not software
At least i keep good parts for the other N900