This is an emergency health kit you can use to heal yourself or others during combat.
Left-click the Startup Health Spindle to pick it up, and place it in your shortcut bar for easy access.
To use the Startup Health Spindle on yourself you must first press F1 to target yourself.
Right-click the Health Spindle icon, or press the appropriate key on your keyboard to use the kit (1-10 depending on where in the shortcut bar you placed the icon).