Yesterday woke up with dizziness when sitting up from bed, which recurs when i tilt head, eg look up. no problems otherwise eg during run. same, but less, today. is this an emergency, should i refrain from exercise?

Depends: This sounds like benign paroxysmal positional vertigo but there are other conditions that can mimic this. You should get evaluated by an ent. This is an emergency if you have other symptoms like speech slurring, weakness, vision problems etc

Dizziness: You may have Benign Paroxysmal Positional Vertigo. This a problem with the inner ear. Movement of the hair cells in the canals are exaggerated causing vertigo on movement. The problem at times will subside by itself. Physical Therapy is helpful also. If the vertigo persist see your MD. You should refrain form excercise that exacerbate tthe vertigo.