Write 'According to Wikipedia' in a PhD thesis I am writing a PhD thesis in robotics and I was wondering if it sounds good to start a phrase with: 'According to Wikipedia ...'

Do you think I can do that or not?
"According to some unknown guy on the Internet, I can say that according to Wikipedia..."

No, you should avoid that. Wikipedia is open, so it can be changed by (almost) everyone and you have no guarantee that the given information there is correct. While many articles are very informative, it might be better to take the actual source (given on the Wikipedia page) and make sure that this source is credible (e.g. published in a good, peer reviewed journal).