Whether to take a holiday or get research experience when transitioning from masters to PhD? Background:
I'm in a precarious situation.

I'm currently in the sixth semester of a ten-semester (five-year) combined bachelor's/master's program in engineering. So far I've had two relevant industry internships and have been getting stellar grades, but I lack research experience in my field. I am still unsure if I want to pursue a PhD, and I'm a bit apprehensive to make that life decision now.

All six semesters I've been taking classes and conducting research in a not-so-relevant field (mainly because research in my field is hard to get as an undergraduate) - suffice it to say after three years of this, I've somewhat burned out.

I'm currently signing up for classes for my seventh semester, which is the first semester I'm required to take graduate classes. Because I've felt a lot of academic pressure, I decided to sign up for less classes than usual to give myself a respite.

In response to this, my academic adviser recommended that I conduct research at a lab near campus to prepare me for a prospective PhD. I'm reluctant to agree because I wanted to take the semester to relax and pursue various interests I've fallen out of touch with since the start of university.

I voiced my concerns to my adviser and he is continually trying to pressure me to conduct research, citing that not doing so would be a huge missed opportunity and might hurt my chances of applying for a PhD.

Question

I don't want to leave this as an open-ended question (a la "what should I do?"), so I'll try to make it more structured: 


How important is having research in a relevant field when applying to PhD programs? 
Would PhD programs look unfavourably upon taking a semester to "relax," considering that a PhD requires a great deal of dedication?
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.