I have a 2000 f150 when i idle it shakes pretty bad but not when it idles in park. if i give it gas it also shakes really bad.
today i realised theres a pully under where the radiator fan pully is and it will start spinning then randomly quit over and over
plus my truck idles really high up for about 3 minutes then dies down alittle

 

Maybe it's the harmonic balancer or the fan clutch going bad, either one should be replaced ASAP, stop driving it until you get it fixed.

 

can you describe where these are?