I have Quectel LTE USB Modem connected to Raspberry Pi 3 Model B+ and able to access internet from modem. Now, ifconfig has wwan0 connection with IP. I want to start hotspot on Pi and share the internet to devices connected to hotspot. Any guide/resources available?
You can use systemd-networkd to create an access point and connect devices on it to the internet. In addition you can also do it with devices (maybe your laptop?) connected to the wired port eth0. How to create this "complete" solution you can look at How can I set my pi 3 up to be WiFi AND ethernet router simultaneously?.
The example there uses the interface name usb0 instead of your wwan0 but from the networking view there is no difference. Just replace usb0 with wwan0 and it should do.