Definitely frowned on. In the main, people go to nude resorts to get back to a “garden of Eden” state: to liberate themselves from the norms of a society that equates nakedness with sexual display. On nude beaches, it is a big no-no for a guy to allow himself to get visibly excited. It sets off perv alarms and could result in you being banned from the beach. The biggest thing you have to remember here is that, unless specified as otherwise, naturist/nude holiday spots are not adults-only zones. They are family spaces: naked parents holidaying with their naked kids.
The reality of being naked amongst nudists is that initially you will be so scared of getting excited it will kill your ability to get hard at all. Once you get past that stage and start to relax, you should be sufficiently used to being surrounded by bare flesh that it won’t happen - and of course, you’ll be making damned sure you don’t let your brain stray into erotic wish-making territory anyway.
I think the most important question you need to ask yourself is “what is my motivation for wanting to be on a nude beach?” If you’re concerned that the experience may be too much of a turn-on for you, then - unless you’re booking into some sort of specialist resort that caters for the swinger/sex party trade - you’re probably doing it for the wrong reasons.