I need help I have put together all new stuff on my computer a brand new build but every time I try start it up no input to the screen so can not go into bioss set up plus it keeps rebooting after 5 seconds
I think you need to recheck your build go back take everything out and make sure everything is connected properly.
Also check the jumper on the motherboard for the bios, make sure its not in recovery mode.
Well you have given very less information. Since its a new build anything can be reason for the restart. To fix it you might need to rebuild the whole system again, but before doing that you can do a few things:
1) Plug out all power source connected to the PC like remove the power cable from PSU.
2) Re-install the RAM and the GPU. Try watching video on youtube for tutorials.
3) Re-plug all the power pins (power you are connecting to the motherboard)