We've all been there - midway through an improvised bluesy or jazzy solo and it just feels totally stale and even though the notes you're using are correct it just feels - meh.
Here's a tip that Warren Haynes shared that he got from Miles: When it's feeling stale, reverse your phrasing. Be silent when you would normally be playing and play where you would normally leave space. It's an amazing trick. Every time I use it within a few bars a new, interesting motif arises (condenses from the aether?) and it's off to the races usually accompanied by a huge smile from the bass player.
Just thought I'd share. It's bailed me out several times. Try it, you'll like it.
Chuck