Good idea to start PhD with a potentially obstructive medical condition?
Part way through my PhD I was diagnosed with ovarian cancer, requiring major surgery followed by chemotherapy. I went to one course unit for a quarter, so that I kept my connection to the department and parking pass, but was not expected to do much work.

I don't know whether the school where you will be doing your PhD will allow that sort of option.

I agree with the advice in comments to discuss with whichever professor is responsible for first quarter students.