Hi
my mom has a similar problem with one of her foster boys. he is 5 now and was potty trained no accidents etc for quite some time. nothing specific has changed in his life but he started wetting his bed several times a week. he would wake up enough at some point in the wetness, to turn around and reposition himself at the other end of bed and go back to sleep.
what they have done is one cut out all sodas, stop his liquid intake after certain time, i believe 6 and he goes to bed at 8. then her husband gets him up around midnite and walks him to the bathroom, he goes potty and then back to bed, hes still half asleep as he walks down the hall to go! part of it can be laziness and tiredness combined, hes tired and sleeps harder and he doesnt want to get out of bed. (they set their thermostats so its colder in winter, heater is lowered and warmer in summer, a/c isnt as blasting at night, so it could also be not liking to get out of bed in cooler temp)
he also wears pullups. i have seen a new type that lets them feel it when they wet, i think thats a better one so they realize it, yet it saves the bed-which she also has a plastic cover on)
these kids are also not around their dad (or mom) much but visits dont seem to affect the potty situaton, just their behavior is bad after visits)
he showers at night and hates that if he wets he has to get a shower in morning too)