Laptop monitor comes on dim?

I ask this before once but been busy to get this thing fix and my friend is out of town that usually fix it. The reason I am asking this is because I notice something that it did but let me explain the current status of it. It is a Dell Inspiron 8600 about 3 years old lately when I power up the computer monitor comes on completely dim but white/bright objects are viewable. Nothing wrong with the hardware that I can see when starting up. Sometimes it can come on fine and stay on and not have a problem until I shut it down there might be a chance the monitor will be fine or not. I did a diagnostics and of course when its dim the inverter lamp fails and when its boots up fine the test p no surprise there. However I can control for it to come on if I do a reboot when the dell logo prompt screen. I really do not understand it but rebooting my hdd drive or anything can bring the screen up every time I tried shutting it down and it comes on fine then maybe 6-7 times of restart dim again.