Random races are, as you might know, a unique feature to this server where, every single lap, you get a random car to drive! It may be a random car in a class or an entirely random car. At the moment, this is completely random - you can get the tractor, the surf van and the air tug while someone else gets the adder, the t20 and the [insert sweet hip raddest car here]. This means that you really shouldn't take random races seriously, as it all comes down to whether the really big dice in the sky like you or not.
However! Random races can be very good practice, and you shouldn't just go ramming people and being a dick. You'll often be in a fast car passing lots of slow cars, or perhaps in a slow car with a couple fast cars battling behind you. This is a perfect chance to figure out how to make an inevitable pass happen without anybody getting hurt, and this will help you in the future when you're dealing with real multi-class races or even just dealing with a slow driver that's speeding up after a crash. You'll find out what methods work best for you, but as with all things in racing give people more space than you really think they need! It might feel stupid to go around the outside of a truck when you could just blast by at a million miles an hour on the inside, or you might feel grumpy about taking an extra long line as a slow car just to let a few people pass by you but remember, the time lost being a clean driver is almost always less than what you lose in a crash.