My check engine light goes on and off especially on long road trips. Can anyone advise?

 

Welcome to the forum.

You need to get it scanned to see what, if any, DTCs are set. Most auto parts stores will do this for free.

 

The light going off and on could be due to the fault setting and then going away at the next key cycling... good chance its emissions related... but as 73shark suggested, getting the codes read will be the best place to start...
There may be multiple codes so write them all down and have them cleared, address those that come back after being cleared, it may take several drive cycles to get them to come back....

Make sure your gas cap is on correctly and is clean and tight fitting... hearing it "click" several times when being tightened is what you want...also make sure you are not over filling the gas tank when filling up...stop at the first click/shut off of the nozzle when is nearly full.