Can he do that, or is the decision not his alone?
I don’t know the wordings of his resignation letter, but if he only resigned from the current term then he can get back to the next term since he was elected for that term as well.
A related but different situation is Democrat Adam Schiff that was elected to Senate twice in November: one to fill the current term and the other for the term starting in January.
It’s his. He won the seat. He gave it up and DeSantis was going to choose a replacement but has not yet done so. Matt can change his mind and take the seat.