Will carbonated beer re-FERMENT?

Here is my issue. I did a octoberfest lager, one of my first ever lagers and looks like I injured the yeast by high pitching temps or what not. Only got down to 1.038. It was a pretty big beer so which is also kinda a first so I didn't know it would be as sweet as it was. I just force carbed it in my keg and tried it after a while. I wanted to try to save it so I repitched some yeast in to see if I could drop it more but the fermentation really will not start. I really wasn't sure if it would or not be carbonated but thought I would try it. Any thoughts are appreciated. Thanks.

A couple of issues you have going on here.
First, it is very difficult to get fermentation going again unless you pitch some actively fermenting yeast (like from top cropping).
Second, Sounds like you racked it off the yeast when you put it in the keg... probably didn't matter though as it sounds like that yeast was done.
Third, the carbonation won't bother the yeast, but the pressure will. So just vent the keg.

Carbonation or not, if there are fermentable sugars available then the yeast will eat them if they can tolerate the environment they are in. As already stated, you may need to vent the keg if the yeast take off again.