if you want it to move nonstop you can use looping command.
Not knowin your overlay size and position nobody can make you exact code for it but I can give you example which you can test in your portal:
INT. BEDROOM - DAY
&overlay BABY FOOT SWADDLE create
&overlay BABY FOOT SWADDLE shifts to 47 58 in zone 1
&overlay BABY FOOT SWADDLE scales to 0.587 0.587
&overlay BABY FOOT SWADDLE moves to layer 1
@overlay BABY FOOT SWADDLE opacity 1
&overlay BABY FOOT SWADDLE shifts to 52 59 in zone 1 in 0.05 THEN overlay BABY FOOT SWADDLE shifts to 47 58 in zone 1 in 0.05 loop infinite times
LOL I had to make the video of it. 
Since not having clock overlay I used the baby swaddle 