Club car won't go

I have a 2005 club car precedent. Recently it has been acting up. It's a 48 volt electric cart with the original batteries, which I plan on replacing this year. Sometimes it just doesn't go. They batteries can be fully charged, the direction switch in the forward position, but it won't go when I press the pedal. If I let the pedal up and try it a few times, then it usually does go. Any idea why this is happening?

Thanks, Dan