Question Laptop Shutdown Issue

[vijinvijay]

I am facing a strange situation with my 10 year old Toshibha C660 laptop. It automatically power off after few minutes when started from long idle and within few seconds immediately after previous shutdown. This situation is seen in BIOS also. On one day I could successfully reset windows but the problem continues. I changed the processor, tested hard disk, fan, RAM, Adaptor, battery and I feel that all those components are working fine. Any idea about what might be wrong? Thanks.