I have been having an intermittent issue. When I leave my 2006 F350 diesel idling for any length of time, when I try to drive away I have no response from the accelerator and it will only go as slow as the idle will allow. It will remain that way for about 20 minutes and then it will slowly return to normal. If I turn off the truck and let it sit, when I turn it back on it is fine. Any thoughts on what might be wrong?

 

There is a number of possible issues.... Some examples are
Your throttle sending unit could have an intermittent fault
No throttle could be your truck is gone into a protective mode.
Check for codes.