Hi everyone, my apologies if this is a stupid question!

Basically last night I was lying in bed at my usual time of 11pm.
I was practicing some self awareness and as I relaxed my eyes they began to jolt back and forth and kept spazzing all over the place!
This isn't something I've noticed before, though it may not be the first time.

Any idea of what this is?
Could it be REM? Though I know it takes a few hours of sleep to get into that stage

Many thanks!