I use scales both hands doubled. Then in harmony starting out two notes with the right hand then joining in with the left hand. I start the scales in c and then do them through the various keys. c, g, d etc. (circle of fifths) up and down. Next I do a few four finger chords broken. You don’t need music to do that and it’s a quick and efficient way of warming up.
I do several versions of scales with the metronome on, and increase the speed to the point where I am challenging myself. I throw in some chord inversions, hand-over-hand arpeggios, Salzedo’s Conditioning Exercises, one-handed arpeggios, then if I have time, I’ll open up Larivière at a random page. I also use bits of tricky orchestra parts or concertos as warm-ups sometimes.