Reward charts for bed wetting?

[pantshavenames]

DS (nearly 4) wets the bed at least 50 percent of the time, usually about 5 or 6 in the morning. This seems to be a new development as he's been out of nappies at bed time for about 8 months. I don't know whether things like reward charts might work to motivate him or whether it's so out of his control it'll just make him feel bad IYSWIM. We've cut back on his bedtime drink but he doesn't drink that much then anyway.
I feel a little out of my depth as I know he's not old enough for it to be an issue but at the same time I don't know why its happening now if it didn't at the beginning.

Any thoughts anyone?

Well my dd1 who is 8 years, still wets her bed when either stressed (hates her Daddy working away) or very tired so a star chart wouldn't be any use for her, would make her feel bad I think. DD3 is 5 years but wets her pull ups every night but she'll stop when shes ready, never had a problem with dd2 yet to find out with dd4! Sorry not much help but I know if I stress about they will feel awful. Good luck!