To me, this sounds like you are using an induction hob which isn't putting in enough power to reach and maintain temperature. My guess would be it is only reaching a simmer then briefly cooling in this cyclical fashion. simmering starts around 85C so would take longer to cook food (pasta in this case).
On the assumption that it is an induction hob; often one ring is a lower power rating so simply altering which ring you use may be a solution to the issue. Otherwise increase the power/temperature on the hob if possible. The third option would be to use a smaller pan or only half fill it so the hob can put in enough power to bring water fully to the boil.
A last suggestion would be that this pan may not actually be stainless steel but another alloy which doesn't heat as well. In this case you can buy induction plate converters which allow less conductive pans to heat more efficiently