Whether to take a holiday or get research experience when transitioning from masters to PhD?
Wanna relax, then do so. Don't be somewhere you don't want to be. You have to be mentally ready to do a research. I have seen many cases of young intelligent individuals who started doing PhD, and then for various reasons gave up, because some serious work needed to be done and they want to have well... some fun (rightfully so)!

I would recommend do not burn the bridge with your supervisor as you might start doing PhD in upcoming years. Tell him/her in a meeting that you would like to finish your studies and enjoy life a little bit; before committing yourself to doing research.