You're getting older, friend, and morning wood is a young man's game. Many men don't get it at all. It's not important if you get it or you don't get it. It's a nothing burger, in other words, just something that sometimes happens to young men as if they keep a schedule that gets them up in the morning that's when most men's testosterone is highest. It's not a sign of health or ill health or anything. The test is, when you have sex with a partner, can you get and maintain an erection? If so, there's nothing wrong here in that area. If you're taking a multivitamin, okay, but if you're supplementing with individual supplements, some of them you can overdose on, so do be careful with dosages. Selenium and copper and chromium and zinc are all toxic if you take too much, but most multivitamins, especially if it's just a one a day, won't really have much and if it's not a very high quality vitamin company the form of the minerals is probably not one that is all that well absorbed anyway. When you're young, you really don't notice poor nutrition all that much just as you don't notice doing exercises wrong or getting too little sleep or a host of things that you will notice when you get old when it catches up to you. If you do in fact require a mineral supplement rather than just want one to maximize health then your diet is leaving you malnourished. Many vegans and vegetarians are under the mistaken assumption that eating that way is automatically healthy, but it's only healthy if you eat a balanced diet high in whole grains, veggies, and get sufficient proteins. The veggies are where the minerals are, and a good variety of them, especially green leafy veggies, should give you enough minerals for health. Sometimes if we body build or play a sport that requires extra muscle or exertion we need extra nutrients, and graduate school as well can be hard on our systems if the school is a high quality one because they load the work on and that doesn't leave a lot of time for eating properly, but when you graduate you fix that. You don't say what you eat so we can't really comment on how you can improve your diet. From your description, you sound like a healthy guy in good shape who exercises regularly but has a misconception of the importance of getting an erection in the morning, so let me assure you, most men don't get that, it's a teenage thing for most of us and then only happens occasionally after that. Not something to worry about.