Befuddling Situation with Outlets

Our church is having electrical issues. We are a small congregation. Our service is 200 amp and it is a Homeline box. The building was built in 93 so all wiring is only 20 years old. All wiring is minimum of 12 guage. We had a series of outlets go dead without any breakers resetting. My F-Law is a retired electrician but lives out of the country. He was here briefly and checked the breakers and said he thought they were good. My son and I were vacuuming tonight and an outlet on another series went dead. I moved the vacuum plug and vacuumed for another 5 mins and that one went dead. I went and checked the breaker box and no breakers were blown. There is no burning smell & I have thrown all breakers off and back on. Anything that stops has not started working again.