We have the same problem.
I am willing to run for Pres again, and my VP will run if nominated, even though she'll be very pregnant/have a newborn for most of the school year. My treasurer is very good and willing to stay again. We have co-secretaries, and neither really wants to do it again, which is fine with me, because they are both great volunteers who could serve us better by chairing things. One of them will run if nominated.
After next year, the board has to vote unanimously to allow me to run past a second term. I really hope we have someone to nominate so I don't have to. I wanna be a regular volunteer, too.
The best we can do is work to develop a culture within our PTO where people are comfortable when they first get involved. Their involvement should grow to the level to which they are comfortable. Hopefully, a few are comfortable leading. It is a slow process.
I did see my stint as president of this PTO as a 2-year project, and we are ahead of where I thought I would be. 110 members, but no new officer candidates.
If we can swear in a new Pres next May, I'll be happy.