A tight sense of rhythm is among a bassist's most important skills, so investing some time as suggested above is a very important use of practice time. It is among the most important basic fundamentals that you want to get right from the beginning, just like good left and right hand technique and learning your way around the neck. You can do everything else well, but if you have inconsistent timing, you'll never really succeed with other musicians. And just like everything else in life, some things come very naturally to some people, and other things come naturally to others. It is a skill that most anyone should be able to improve with practice. If it is something that you need to improve, you will never regret the time you spend working on it.
I prefer playing with drum tracks over a metronome when working on timing. To me, it just feels a little bit more like playing with another musician. I've been playing long enough and it's ingrained enough that I don't have to do a lot of work with the drum machine now, although it is useful at times when learning a new riff, in that you can slow the drum track down to learn the tricky parts, then get it up to speed.
Enjoy your journey deep into the land of Groove!
I prefer playing with drum tracks over a metronome when working on timing. To me, it just feels a little bit more like playing with another musician. I've been playing long enough and it's ingrained enough that I don't have to do a lot of work with the drum machine now, although it is useful at times when learning a new riff, in that you can slow the drum track down to learn the tricky parts, then get it up to speed.
Enjoy your journey deep into the land of Groove!

With a metronome it's obvious...you have to provide the groove yourself. You can use a drum machine as a metronome, though, by programming patterns playing only rimshots. Just avoid those "Santana in a box" patterns 
, etc.