My baby is 5mo and lately he has getting up at night (after a month of getting into a napping routine). He just plays and then sleeps after a good 3-4 hours. What should I do?

Babies go through many phases of sleep patterns. This is just one of them. You must understand that your baby too is trying to adjust to your routine. Some changes are bound to take place but rest assured this will pass soon and your baby will start sleeping full nights in another 3 to 4 months. If you are feeling sleep deprived try and catch a nap during the day alongwith him :)