There is a lot of stuff you can do to warm up. You can decide for yourself what works for you and what doesn't.
Scales
Scales are something you should always warm up with even if you hate them, which you probably do. You can practice scales from a piece or étude, one you have been working on recently, one you need a refresher on, or a chromatic scale. A chromatic scale is a scale that goes up by half steps, hitting every note. These are nice to practice so you can get a feel for the keys or fingerboard, not very fun to listen to though.
Stretching
This might seem a little stupid to you, and it kind of is, but we stretch every day in orchestra. It helps me remember that playing requires your body not just your mind. This makes me mindful my posture and range of motion. Also kind of amusing when people see you stretching before you play and give you the weirdest looks. It's hilarious.
Old Pieces
It's fun to look back on the old things you played and get a little nostalgic...that might just be me. Either way practicing old stuff keeps your reptoire fresh just in case you need a piece for an audition or recital.
Instrument Specific Warm Ups
One thing you can do to warm up for stringed instruments is to play scales or open strings at different tempos and patterns. It helps to use simple fingerings so you can focus on having your bow arm move how it should. If you play a wind instrument you can do the same thing to warm up your lungs and tongue, except you know with your mouth.