Biphasic sleep and REM sleep

So I started working a night shift and I usually sleep in the day, but since I like to enjoy the day I started a biphasic sleep but of my own, not the 4-5 hour sleep plus the nap. Mine is more like 3-4 hour of sleep and then later another 3-4 hour of sleep.

I was just wondering if it causes sleep cycles to change because the other day as soon as I started sleeping I went to REM sleep, I know because I was slighty aware of my dreams and woke up with hot temperature, slighty sweaty and with a fast heart rate. Basically the whole divided 8 hours of sleep seemed like REM sleep. One thing though is that I was probably sleep deprived, sometimes I don't sleep much.

Also, with this biphasic schedule I seem to be able to go to sleep instantly, even if I'm not tired. I can be euphoric with high energy, then sit down and in less than 5 minutes completely relaxed and in another 5-10 minutes completely in trance or asleep.

Are these the benefits that biphasic sleep gives?

I have never been on a very irregular sleep schedual but I know why you had a lot of REM sleep. What you experienced is called REM rebound. Because you did not get enough REM sleep (which comes in cycles after being asleep 3-6 hours) When you do not get enough REM sleep your body enters the rebound to try and compensate. I don't know if this will sort itself out or not. I wouldn't recommend it.