It's not like you need literal years of community service but volunteer work, especially done in a clinical setting, is relevant to a good medical school application. It's best to have a long-term commitment for a variety of reasons: demonstrates commitment, people at the service get to know you very well (LOR potential?), you are very familiar with the work and can speak reflectively and authoritatively on it, etc. For those reasons, it's pretty standard for people to recommend to find something that is available, interesting, and meaningful to you and do it once or twice a week (or more, or less) throughout undergrad.