Almost every time i take a nap i have a dream. But I remember reading somewhere that your body need a certain number of hours before entering REM so how can I have dreams in less than half hour naps? 
I used to be a firm believer that you need to be in R.E.M sleep to dream but as of late i have had midday sleeps which i know i am only asleep for about 30minutes and have had alot of dreamtime,so i’ve changed my perspective.
That’s not really it.
During naps you skip parts of the sleep cycle such as deep sleep. You’ll enter REM very quickly and easily during naps. THAT’s why it’s so easy to have dreams. It’s not because you dream outside of REM or anything.
For some reason I dont dream while napping. Anyone know why?
Yeah, me neither! 
No idea why though.
Some people dont “dream” in their nap because their usually very tired which is a deep sleep. So technically its not the natural “nap” your getting.
I would recommend napping around 6 hours after you’ve waken up to experience dreams 
I’ve been having a dry spell lately with LDing… but I just recently found out that I’ve had the most success I’ve ever had when I take a nap. Whether it’s WILD, or MILD, it just works for me… they are a lot shorter and sometimes are pretty weak in comparison to night LD’s but I’ll take it.
There’s a nap experiment going on at the Lucid Labs:
https://community.ld4all.com/t/exp-polyphasic-sleep-naps-and-lding/31296
There’s info on the right time to nap and more, and someone might want to join.