I have a warning light which is an orange cog with exclamation mark inside which comes on the then the engine goes into a limp mode. It resets on turn off/ on. but keeps happening on irregular basis

It has detected a malfunction and it is trying to save your motor from damage. that is why it wont rev or gain power, it doesnt want you to. kinda like you just broke your leg and someone said get up and walk, yet your brain says no its gonna hurt or fail causing further damage. Could be a oil pressure,cam sensor,knock sensor, temp sensor. need to get a diagnostic check on that car, I dont think its a major issue if your car is running and you hear nothing out of the ordinary, I'm not saying to drive it either, It needs to be checked now to protect the motor and your pocket book.