We usually prefer specific questions that allow specific answers here, but I'll see what I can do...
There are lots of bikes in a huge variety of types out there for sale. To narrow it down, you should at least start thinking about a few decisions:
- How much are you able and willing to spend?
- Where will you keep the bike? (When I was a student, most bikes had to stay outside in all kinds of weather. If the bike has to live outside, I wouldn't recommend anything fancy, because bikes kept outside rust.)
- How will you secure the bike? (If you can't park it in your room at night, then I wouldn't recommend anything fancy, because fancy bikes stored in public areas disappear, whether they're locked or not.)
Then there is the big spectrum with road bikes on one end, and mountain bikes on the other. Stereotypical road bikes have skinny tires, curved handlebars, and no shocks; they're designed to go fast on roads, and are usually terrible on gravel. Stereotypical mountain bikes have straight handlebars, fat knobby tires, and often have shocks (called "suspension" in the bicycling world); they can handle all sorts of terrain, but are relatively slow on the road. Mountain bikes are generally built to be sturdier than road bikes.
These days there are all sorts of bikes in between road bikes and mountain bikes. For instance, gravel and cyclocross bikes look like road bikes and have curved handlebars, but fatter tires with more of a tread pattern that can handle dirt and gravel. Hybrid bikes look like mountain bikes with straight handlebars and an upright seating position, but have skinnier tires for better performance on the road. (It should be said that you can put skinnier, less-knobby tires on any mountain bike.)
Then there's new versus used. New bikes are great of course, but your money doesn't go as far, and lack of money often pushes bike buyers to buy lesser-quality bikes that don't last, which we often call BSOs here, for example bikes from Walmart. BSOs aren't so terrible, I rode them for years, but they do break down faster and are harder to maintain.
You can get a lot more for your money with a used bike, but it's easy to get ripped off when buying a used bike. Someone who really knows bikes could be very helpful when buying a used bike.
So here are some arbitrary recommendations:
Because you're heavier than the average rider, and because you haven't expressed a clear preference for a road-style bike, I'd recommend a mountain bike or a hybrid, because they're sturdier. (Quality road bikes can be sturdy, but quality can be expensive for road bikes.)
If you have to keep the bike outside, get a cheap (BSO) mountain bike or hybrid. Try to get the right-size frame; look for a frame size chart online.
If you can get good advice and you can keep the bike inside, get a good used bike. I'd recommend a "hardtail" (no rear suspension) mountain bike or a hybrid. (Suspensions look cool but rob your pedal strokes of power, so in my opinion it's best to avoid them unless you need them. The front suspension can be switched off on most good mountain bikes.)
If you have plenty of money and you can keep the bike inside, go to a bike shop and try all different sorts of bikes. Unfortunately this option is not very practical in the COVID era, because bike shops usually have very little inventory, and typically all the popular models are sold-out.
Some general advice: wear a helmet, get a good tire pump, and learn how to do your own bicycle maintenance if you're at all mechanically-inclined.
Bicycles are wonderful things. There's a joy to riding any bicycle, and you'll be healthier getting places under your own power rather than riding in a car or a bus.
