I had first to look up the term appositive. I think it is the same as apposition.
An example for appositive/apposition is:
The beast, a big lion, was slowly approaching.
Appositions after a noun give more detailed information about the preceding noun and
are usually separated with commas.
I doubt whether the gerund groups in the above posts are appositions.
In the sentence "I had problems starting the car this morning" the gerund group has the function of a sub-clause such as when I was starting the car. You can shorten this sub-clause with a gerund: when starting the car - and you can drop the conjunction and only say "starting the car". In my view these gerund groups stand as adverbial sentence parts and not as appositions.
Interested by this problem I checked my two grammars (Longman, L.G. Alexander and Oxford, John Eastwood) and I was
really not surprised that they don't mention the use of gerunds as adverbial sentence part at all.