If you want a gradual increase in speed with only 2 keyframes, you need a bezier keyframe or easy ease keyframe for the first keyframe.
Select your first keyframe and press “shift + cntl+ F9”, that will create a slow ease out of the first position. If you go to graph editor you can use the handles to determine how slow it takes to ease out of the first position.
Johnny Cuevas, Editor
Thinkck.com
“I have not failed 700 times. I have succeeded in proving that those 700 ways will not work. When I have eliminated the ways that will not work, I will find the way that will work.”
—THOMAS EDISON on inventing the light bulb.