“Check Engine”

Hello, it’s me again… …. at my 900 convertible, EZ 03/90, 126 HP, lights up the check engine light shortly after the start, for about 2-3 minutes, then extinguishes again and the car drives normally. During the luminous display it does not seem to get optimal fuel (pump, plugs are replaced). Does anyone know advice???? Thanks already now, smokeyjosephine