Cats are quite sensitive,and if anything disrupts what they are used to it can be upsetting for them. So yes, maybe a dream...or an unusual noise, an insect...anything.
My boy sleeps regularly in certain spots...my bed, the guest bedroom, sofa and big chair. After the last time my daughter and her partner visited over a month ago, he's not gone into the guest room...and it was several weeks before he slept on the sofa.
Cats will often sleep in the same spot for weeks...and suddenly have a different favourite place...that's them being cats.
Your cat will go back to his normal when he's ready.