BodyForce works in air, but super slow on ground?

I'm trying to make the player automatically move in the direction they're looking. I currently have a BodyForce object inside the Torso, and I'm just setting the Torso's lookVector to the BodyForce, and it propels me super fast in the air, but not on ground. The script is in StarterCharacterScripts.

Script:

wait(0.1)
script.Parent = script.Parent.Torso
while true do
    script.Parent.BodyForce.Force = script.Parent.CFrame.lookVector * 5000
    wait(0.1)
end

I've tried setting the friction on the legs to 0, but that still didn't work.

edit: I can jump and I'll still move super fast for 3 seconds but then it goes back to super slow, and changing direction stops that.