Hello, just want to preface this post by saying I am very ignorant about cars and how they work

My 1989 240 wagon has been having some issues for some time. When turning it on, it does always turns over initially but within 2 seconds it will fall back to revs. It seems that the only way to keep it running was to rev the accelerator for a while and then it would drive okay. For the first 5 minutes after driving while idling (at a red light for example) I had to give it a little bit of revs to keep it from stalling. After 5 minutes or so of driving it would not have any problems. However, turn it off and the same issue would arise

This was happening for a little while and I took it to a few mechanics who all told me that they solved the problem, just for it to come back shortly after.

Fast forward to now and the car does not start even with a few revs. It will turn over but within 2 seconds turn back off – even if I apply the accelerator.

Can anyone identify the source of the problem here?

Thank you.