Dodge Stratus Trip Computer Error?

I drive a 2004 Dodge Stratus SXT. Tonight when I was driving home on the highway my car did the "ding" noise it does when someone has opened the door. When I glanced at the instrument cluster to see if it had said a door was open; I realized that my trip computer had automatically reset itself. It had just been reset yesterday when I purchased gas, so it hadn't reached but maybe 100 miles. This is the first time something awkward like this has happened. Any suggestions as to why this happened?