What if any are the side effects of suddenly going off androgel?

Andropause symptoms! Your testosterone levels will decrease, and that will make you feel tired, and possibly have hot flashes. This usually improves after few weeks, especially if your body was able to produce it's own testosterone.
Depression/Suicide. Typically, testosterone supplementation shuts down what little testosterone you were making at diagnosis prior to treatment. If you stop your supplementation abruptly, regardless of methodology, your testosterone level will be non-existent for a while before your body kicks back into gear and returns to baseline (inadequate) production. During this time, you're susceptible to depression & suicide.