wet sparks plugs?

I have a 1993 toyota previa minivan . but sometimes when I start it the van wont start, I check the sparks plugs and they were wet with gas . I dry them out,put them back and the van start it just fine .. but now is doing it almost every day. It does it ither hot or cold,, Is a toyota previa 2.4 4cl. 1993 ..... I appreciate any help I can get thank you