Short of breath when i first start exercise but after warming out it become fine. is that a sign if heart disease or is it normal?

Possibly, lung issue: more likely, e.g. mild bronchospasm/asthma (↓es air out thus making getting more in progressively more difficult), when not exercising which eases after warming up. While bronchospasm ↑ing during exercise gets more press, these are individual behaviors & vary. In you situation, easing of bronchospasm more likely than advanced heart Ds. Also study: https://www.healthtap.com/#user_questions/1574549.