Well congratulations for getting back into an exercise routine after such a long period of inactivity! The hardest part is redeveloping the routine, but once you're there, training will become second nature.
It is certainly normal for your muscles to feel like jelly after a workout, especially considering how long you have been away from any training. Your muscles have been completely de-conditioned to exercise (be it cardiovascular or resistance training), if you have been leading a sedentary lifestyle.
The fact that your muscles feel normal within a couple of days could indicate a very rapid rate of recovery. This isn't a bad thing - your muscles may just be quite resilient to the trauma that causes muscle pain. Another explanation could be that you are not working the muscles hard enough to cause sufficient stimulus.
A rapid rate of recovery does not indicate overtraining. There are many signs of overtraining - check out a blog post we have available on how to recover from exercise. However the most distinct sign of overtraining is that you are not making any progress - whether that be not gaining strength, losing weight, improving fitness etc. Of course, just because you are not making positive progress does not necessarily mean that you are overtraining as there are many other key factors to watch out for as detailed in that article.