I have a 2001 Buick Century with 125,000 miles on it. Lately, and only when I am in traffic with lots of stops and starts, the engine skips and the check engine light comes on. When I turn the car off, let it sit for a few minutes, and restart the problem is gone and the check light goes off. I never have this problem during normal speed driving.
There’s no simple answer to that. If you post some idea of the maintenance history of the vehicle, it would help people try to help you. The typical things that can create problems are things like spark plugs, wires, air filters, fuel filter, ignition coils, etc.
If you haven’t, or don’t have these things dealt with according to regular maintenance schedules (outlined in your owners manual) then start with a basic “tune up” including plugs & wires and all filters.
You should also have the check engine codes read - some chain auto parts stores (e.g. Advance, AutoZone) do this for free. If you have someone read the codes, don’t let them sell you anything, and get the actual code (it is a number preceded by a letter such as P0300). Then post that along with maintenance info.