I'm a college freshman, but was your typical sub-4:40 guy in HS. I stopped running as regularly in college but still jogged a 0-2 times a week. I'm trying to get back to running seriously but whenever I try an easy run, it feels inexplicably hard just 25-30 minutes in to the point I need to walk. I'm not sure if I'm severely undertrained or if it's mental or if I just forgot what it's supposed to feel like. Any suggestions?