Nissan altima 2001 engine/car shakes

nissan altima 2001 possible distributor / manifold gasket failures. Car/engine shakes all over either spontaneously during braking or at stop sign just before take off. also occurs randomly sometimes coupled with poor acceleration. had plugs replaced recently to address this. did not fix.

There’s not enough info known for anyone to even make a wild guess as this could be caused by one or more of a 100 things.

If the plug replacement was a case of throwing mud at the wall and hoping some of it stuck, then that is the wrong way to go about it.
First step is get the car scanned for codes. AutoZone, Checkers, etc. will do this free.
If no codes present then check the fuel pressure.

Just offhand, if this problem only occurs at idle or low RPM it could be caused by an Idle Air Control valve problem.

In addition to a possible igntion problem (have the computer scanned as suggested) this could also be a busted motor mount.

Since it’s coupled with poor aceleration, a vacuum leak is not out of the question either.

The good news is that there are other tools beyond the scan tool that a good mechanic can use to find the cause. However if you bring it to the shop and say “change the sparkplugs” instead of “these are my symptoms…”, then you’r unlikely to get the problem solved quickly and affordably if ever.

Why did you say “possible distributor / manifold gasket failures” - ? Are those your guesses? Or do you have some concrete reason to believe that these may be problems?