93 LeSabre Limited - acceleration problem

My 93 Buick LeSabre Limited has about 116k miles on it. As suggested, I'll give as much info as possible.

I brought it in last month for an oil change (for which it was overdue, regrettably), radiator flush & fill and an overall maintenance check where the mechanic said the hoses, belts, brakes, etc. Looked fine. (So either the car was otherwise in good shape or he skimped on me, as he didn't find a reason to charge me more money!)

The symptom I am having in the car occurs when I am applying the gas pedal, whether to increase speed or maintain a steady speed. The best way I can describe it is a slight hesitation that is like when you suck a shake through a straw and get to a thick spot and it takes a little more effort to suck it through. (Ok, laugh at me, but it's the best I can come up with!) The car does NOT stall or shake or make noise.

It began a few months ago as an almost imperceptible pause when going down the incline of the large bridge I cross every day. Now it has become noticeable when on level roads. There is also increased effort when going up the incline.

I have noticed that it takes just a second longer of turning the key in the ignition to get the car started these days. But once it is running, I don't have problems.

The only warning light I have is the Oil warning light, which flickers when I'm idling (foot on brake), but goes off when I am driving or in park (foot off brake and/or on gas). This started on Easter weekend. May not be related, but noticed it after driving up a river levee and bumping the underside of the car on the pavement when getting back on the road. Did not resolve after oil change.

The hesitation/gulp/sluggishness is now a daily symptom, so I want to identify it and correct it before I have more serious issues.

Help would be much appreciated! :D