Network signal shows no service in iPhones se2

I have been using iPhone se 2 since a year now. Never used this phone for games and no single scratch, a gentle usage. All of a sudden experiencing weird behaviour as the network signal disappears and show as no signal

and in few minutes it shows one or two points even in the good network area

tried checking by exchange of SIM cards

whichever sim I insert in this phone shows the same results

this impacts calls messages unable to use mobile data due to this inconsistency signal

pls help me on this