2014 lacrosse awd - light trottle the car had the feel of it hitting bumps.

no check engine light. not coming from suspension or tires. I was thinking engine, but I dont see a change in the rpms. I know this is crazy sounding. only does it at the higher speeds after 15 mins of driving.

please explain so I can understand why this could be the issue.

A misfiring cylinder feels like a jerking or bucking sensation under a particular engine load or road speed - many people mistake this for a suspension or tire related problem .. Highly recommend hands-on testing by qualified personnel. Many times this intermittent misfire will not set an engine code nor turn on the check engine light .. Professional scan testing will reveal any cylinder misfires during test drive. ▪️https://repairpal.com/repair-shops▪️

The misfire may occur at anytime the right conditions are present - engine temperature - engine load and which gear the transmission has shifted into according to road speed - it may happen only once - multiple times or may not occur for some time - there is no certain pattern. Good luck with it!