O.k then all I got from the service manual on this is an internal failure to be diagnosed.
Depending on the length of times it takes between shut downs , you could be dealing with overheating or temp. sensors or cooling fan.
Without being there myself with tools and meters it would be difficult to confirm any of those .
Perhaps just blowing the dust off the fans would do the trick.
There are 3 fans internally , if you wish to look into this yourself I can upload a page from the manual that will show you were they are located ?
Click this link here "CLICK ME"
But I must tell you that usually there would be a specific error code with the power and lamp light blinking alternately to point to a fan or sensor error.
If you are not into removing the back cover and light engine yourself and would like the help of a local tech. on this then click on the link below and enter your zip code ;
This will give you a list of repair shops in your area. You could give a call to different shops in your area to get an idea of their rates , this is a bit like buying insurances , it pays to shop around.