2008 Ford Fusion fluctuating engine noise

Have a Ford Fusion that while maintaining a speed, (as in just cruising down the road at 45 miles per hour for example cuz that’s mostly the speed it’s driven at) the engine will begin to sound like its bogged down almost like the oil pressure is low. However when making the noise it’s not like there’s a noticeable loss in power and no low oil pressure light kicks on. Once I accelerate again it will immediately stop. Has been getting progressively worse over the last month or two in that it happens more frequently