Right time to start exercising?

Hi everyone! I am 41yo (will turn 42 in Jan) and have an almost 2yo. We started trying for a second baby in August, and I hope to get pregnant by spring time. I would like to change a bit my lifestyle now the LO is in nursery, I work part time and it seems we ha e a good routine. So will just start eating healthier (I do eat proper and healthy food, my problem is snacking and especially in the evening) and I would like to strat an exercise routine, joining a gym and or running. My question is: is this the best time to do so? What is your experience if in a similar situation? Thank you!!