K.P.
It's entirely possible that it's a combination of a new bed/room and typical toddler nightmares. At this age, many toddlers and preschoolers start having very vivid nightmares. They cannot differentiate between "real" and "dream" because they don't have the cognitive maturity yet.
The best advice I could give you is to continue with what you are doing (rubbing his back and putting him back to sleep) and remind him that dreams are not real. You don't say how old your son is, but during the day find out if he remembers waking up or what scared him. This may give you some insight.
When my son was 2, he had horrible vivid nightmares. He rarely remembered them in the morning, but it scared us to death to hear him scream like that. He too would go right back to sleep without issue, but once in a while he did remember. Apparently his nightmares surrounded giant spiders crawling into his bad. We added to our nightly routine so that it included having my husband check under his bed with a flashlight and confirm that there were no bugs.
Now that he's 3.5, the dreams are coming back again. He's reading more books and seeing more movies with scary characters (Disney can be pretty scary), so it's to be expected. We do the same thing, though... my husband puts him back in his bed and rubs his back. In the morning we talk about the fact that dreams aren't real (he is old enough to get this now) and that they are just pictures in his imagination.
I don't think this has anything to do with needing less sleep, but has everything to do with him developing an imagination, which is a good thing! The challenge now is to help him differentiate between "real" and "imaginary". He'll get there and he'll go through this on-and-off for many years.