Seems the easiest way is to put all your favorite songs on a Ipod and then use shuffle. It is like having your own private radio station, without commercials.
Mix tapes are about a lot more than just having your favorite songs in one place. It’s themes, narrative, structure. One of my favorite things when I made them was to change the meaning of a song by what’s around it, you can take a song about unrequited love and turn it into a breakup song if you’ve developed the narrative.