Item with random motion at spawn

I'm trying to apply a random motion to an item at spawn. Since the effect I want is essentially the result of running a /loot spawn but with an amplified range, I tried scaling up the Motion NBT using /execute store result entity @s Motion[1] double 3 run data get entity @s Motion[1] (for all 3 motion values), but apparently entity motion is computed in background at a much higher rate than what we can achieve with function. In short, the item moves a lot before the new Motion is computed and applied. Are there any other elegant solutions to this other than going straight to a random number generator?