Do an activity that you usually do in your native language but try to do it in your second language. For me, this is reading. I love reading so I now read predominantly in my second language. I don't stop constantly to look for the definition of the words and even if I don't understand everything I read, I just keep reading for fun. If the activity is entertaining, you will learn without feeling like you are studying, but you should treat the activity like something fun, not like study time.

Find activities that you enjoy and you'll never have an issue with motivating yourself. It's only when you force yourself to do things that are tedious or boring that motivation becomes a problem. Watch movies and series that you like and listen to songs you like. Watch, listen and read things about topics that interest you. Make language learning fun.

I think you need to understand why you are not feeling motivated. For example, I have experienced loss of motivation from changes in my life I actually felt I was losing motivation studying my target language before but I was just exhausted from all the stress of adjusting to those changes. After I adjusted I was still motivated as ever. But your motivation can be affected by how you learn even who you learn with. Try something new. I always encourage my students to try learning and having conversations with different teachers and tutors.