If the only instrument available is the bass, try finding songs from your favorite bassist that inspired to play when you first started. Remember that excitement? If it is not with those older artists, start searching for tunes that give you that feeling.
I have been there. Took a hiatus to raise a family and it was fairly easy to find that spark. Even when touring and gigging full time years ago, I always pushed myself to develop a wider ear. That helped tremendously in finding inspiration.
I also have learned to play, guitar, mandolin, keys and even drums. Besides those and singing and continuing the practice of singing while playing many of those instruments, there never seems to be a day where I'm not feeling inspired.
We have a gift as musicians that is rare. Find your joy in your playing... You know where and what it is deep inside. I know I know... That came off a bit preachy but for me it's almost instinct and very easy to find.
I must confess to really be enjoying playing guitar more lately. Both electric and acoustic... If you do not play guitar, you'll find it fairly easy to learn. It's only made my bass playing better and I find many bass parts on the guitar.
Last but not least... Gig