Sometimes when this happens it means that there is something that has collision even though you cant see it.
When you are playing your game turn on collisions to see if you are colliding with something. To do this simply,
Start your game when you are playing, press the `/~ key on your keyboard. This will allow you to enter a command.
You will Enter the Command “Show Collision”
This will show everything you are colliding with!
If you find what you are colliding with, just go to its import settings and make sure you fix its collisions. There are plenty of tutorials online on this. Good luck!