I have a uromastic lizard (niger) that has recently started to
violently shake his head whenever he eats or drinks, then opens his
mouth and sticks out his tongue and acts like he is choking.  These
episodes usually last for a couple minutes.  I havent noticed any
other changes except that he is not as active as normal. What can I do
to help him other than take him to a high priced vet?

Respiratory infections are the common cause of what you describe.
I would make sure that the enclosure is hot enough and also that it is
dry enough. Too cool or too humid and you will have this problem. Try
raising the temperature in the enclosure a couple of degrees and see
if the problem persists.
Unlike other reptiles Uro's like things quite hot basking areas should
be close to 120 degrees and the cooler end of the enclosure should be
between 86-90 degrees. Give a small water bowl to decrease the
relative himidity in the enclosure. Substrate should be sand or
gravel.
hope this helps