Eh congrats on your first pregnancy! Honestly, 4 months is the perfect time to start, a few of us dalam circle usually stick dengan simple ones like walking, modified yoga, atau swimming because they're safe and tak perlu overthink. My friend swears by YouTube channels yang specifically made for pregnancy exercise (search "prenatal exercise first trimester"), tapi honestly the best one is whatever you'll actually do consistently, jangan la follow yang complicated then give up after 2 weeks haha. Since you're first-timer, maybe check with your gynae once what's okay for you personally, then pick one senaman and stick dengan it, consistency wins over perfection!