if your destination is to reach ultimately Bhavnagar/near areas and to save precious time
alight at Baroda/VADODara jn(ignore train transit citing time issues,too long route) and take private buses/govt bus or pvt tourist/personal vehicle by road only 194 kms lane highway just 3-4 hrs travel time..
,fast,comfortable most imp save precious time and avoids fatigue of extra exhaust time
...
more... by train mumbai- Bhavnagar is 15-17 hrs time and less trains ,if your coming from mp,north or east/west India side
Vadodara is best option to chain /onward further travel and moreover there are over 50 trains daily from/to Mumbai stations
some pvt bus links
click here click here