Absolutely! Triund is an easy beginner trek. And trust me you'll never actually be doing it "solo" because of the trek's popularity. While on your way up, you'll find many fellow trekkers whom you will eventually be friends with. Here's one trip you can refer to plan your trek better:https://www.tripoto.com/trip/trek-to-triund-5804d4578cccd
If you mean middle of March then I'll have to say not this year as I just came back from Dharamsala. Triund is covered with snow and because of weather disturbance this year it is not possible to camping in Triund though one could go for a trek but one should check weather forecasts before setting out.
Triund is one of the easiest trek in HP. Solo or group both also fine. The climate in September and October is very opt for exploring Himachal. Explore!!